Quantum Shift Register Structures

ABSTRACT

A novel and useful controlled quantum shift register for transporting particles from one quantum dot to another in a quantum structure. The shift register incorporates a succession of qdots with tunneling paths and control gates. Applying appropriate control signals to the control gates, a particle or a split quantum state is made to travel along the shift register. The shift register also includes ancillary double interaction where two pairs of quantum dots provide an ancillary function where the quantum state of one pair is replicated in the second pair. The shift register also provides bifurcation where an access path is split into two or more paths. Depending on the control pulse signals applied, quantum dots are extended into multiple paths. Control of the shift register is provided by electric control pulses. An optional auxiliary magnetic field provides additional control of the shift register.

REFERENCE TO PRIORITY APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/446,294, filed Jun. 19, 2019, entitled “Quantum Shift RegisterStructures,” which claims the benefit of U.S. Provisional ApplicationNo. 62/687,800, filed Jun. 20, 2018, entitled “Electric SignalPulse-Width And Amplitude Controlled And Re-Programmable SemiconductorQuantum Rotation Gates,” U.S. Provisional Application No. 62/687,803,filed Jun. 21, 2018, entitled “Semiconductor Quantum Structures andComputing Circuits Using Local Depleted Well Tunneling,” U.S.Provisional Application No. 62/689,100, filed Jun. 23, 2018, entitled“Semiconductor Controlled Entangled-Aperture-Logic Quantum ShiftRegister,” U.S. Provisional Application No. 62/694,022, filed Jul. 5,2018, entitled “Double-V Semiconductor Entangled-Aperture-Logic ParallelQuantum Interaction Path,” U.S. Provisional Application No. 62/687,779,filed Jun. 20, 2018, entitled “Semiconductor Quantum Structures AndGates Using Through-Thin-Oxide Well-To-Gate Aperture Tunneling,” U.S.Provisional Application No. 62/687,793, filed Jun. 20, 2018, entitled“Controlled Semiconductor Quantum Structures And Computing CircuitsUsing Aperture Well-To-Gate Tunneling,” U.S. Provisional Application No.62/688,341, filed Jun. 21, 2018, entitled “3D Semiconductor QuantumStructures And Computing Circuits Using Fin-To-Gate Tunneling,” U.S.Provisional Application No. 62/689,035, filed Jun. 22, 2018, entitled“3D Semiconductor Quantum Structures And Computing Circuits UsingControlled Tunneling Through Local Fin Depletion Regions,” U.S.Provisional Application No. 62/689,291, filed Jun. 25, 2018, entitled“Semiconductor Quantum Dot And Qubit Structures Using Aperture-TunnelingThrough Oxide Layer,” U.S. Provisional Application No. 62/689,166, filedJun. 24, 2018, entitled “Semiconductor Entangled-Aperture-Logic QuantumAncillary Gates,” U.S. Provisional Application No. 62/692,745, filedJun. 20, 2018, entitled “Re-Programmable And Re-Configurable QuantumProcessor Using Pulse-Width Based Rotation Selection And Path Access OrBifurcation Control,” U.S. Provisional Application No. 62/692,804, filedJul. 1, 2018, entitled “Quantum Processor With Dual-Path Quantum ErrorCorrection,” U.S. Provisional Application No. 62/692,844, filed Jul. 1,2018, entitled “Quantum Computing Machine With Partial Data Readout AndRe-Injection Into The Quantum State,” U.S. Provisional Application No.62/726,290, filed Jun. 20, 2018, entitled “Controlled-NOT and TofolliSemiconductor Entangled-Aperture-Logic Quantum Gates,” U.S. ProvisionalApplication No. 62/695,842, filed Jul. 10, 2018, entitled “EntangledAperture-Logic Semiconductor Quantum Computing Structure withIntermediary Interactor Path,” U.S. Provisional Application No.62/698,278, filed Jul. 15, 2018, entitled “Entangled Aperture-LogicSemiconductor Quantum Bifurcation and Merging Gate,” U.S. ProvisionalApplication No. 62/726,397, filed Sep. 3, 2018, entitled “SemiconductorQuantum Structure With Simultaneous Shift Into Entangled State,” U.S.Provisional Application No. 62/791,818, filed Jan. 13, 2019, entitled“Semiconductor Process for Quantum Structures with Staircase ActiveWell,” U.S. Provisional Application No. 62/788,865, filed Jan. 6, 2018,entitled “Semiconductor Process For Quantum Structures Without InnerContacts And Doping Layers,” U.S. Provisional Application No.62/794,591, filed Jan. 19, 2019, entitled “Semiconductor QuantumStructures Using Localized Aperture Channel Tunneling Through ControlledDepletion Region,” U.S. Provisional Application No. 62/703,888, filedJul. 27, 2018, entitled “Aperture Tunneling Semiconductor Quantum Dotsand Chord-Line Quantum Computing Structures,” U.S. ProvisionalApplication No. 62/726,271, filed Sep. 2, 2018, entitled “ControlledLocal Thermal Activation Of Freeze-Out Semiconductor Circuits ForCryogenic Operation,” U.S. Provisional Application No. 62/731,810, filedSep. 14, 2018, entitled “Multi-Stage Semiconductor Quantum Detector withAnti-Correlation Merged With Quantum Core,” and U.S. ProvisionalApplication No. 62/794,655, filed Jan. 20, 2019, entitled “SemiconductorQuantum Structures Using Preferential Tunneling Direction Through ThinInsulator Layers.” All of which are incorporated herein by reference intheir entirety.

FIELD OF THE DISCLOSURE

The subject matter disclosed herein relates to the field of quantumcomputing and more particularly relates to a controlled quantum shiftregister for transporting particles from one quantum dot to another.

BACKGROUND OF THE INVENTION

Quantum computers are machines that perform computations using thequantum effects between elementary particles, e.g., electrons, holes,ions, photons, atoms, molecules, etc. Quantum computing utilizesquantum-mechanical phenomena such as superposition and entanglement toperform computation. Quantum computing is fundamentally linked to thesuperposition and entanglement effects and the processing of theresulting entanglement states. A quantum computer is used to performsuch computations which can be implemented theoretically or physically.

Currently, analog and digital are the two main approaches to physicallyimplementing a quantum computer. Analog approaches are further dividedinto quantum simulation, quantum annealing, and adiabatic quantumcomputation. Digital quantum computers use quantum logic gates to docomputation. Both approaches use quantum bits referred to as qubits.

Qubits are fundamental to quantum computing and are somewhat analogousto bits in a classical computer. Qubits can be in a |0> or |1> quantumstate but they can also be in a superposition of the |0> and |1> states.When qubits are measured, however, they always yield a |0> or a |1>based on the quantum state they were in.

The key challenge of quantum computing is isolating such microscopicparticles, loading them with the desired information, letting theminteract and then preserving the result of their quantum interaction.This requires relatively good isolation from the outside world and alarge suppression of the noise generated by the particle itself.Therefore, quantum structures and computers operate at very lowtemperatures (e.g., cryogenic), close to the absolute zero kelvin (K),in order to reduce the thermal energy/movement of the particles to wellbelow the energy/movement coming from their desired interaction. Currentphysical quantum computers, however, are very noisy and quantum errorcorrection is commonly applied to compensate for the noise.

Most existing quantum computers use superconducting structures torealize quantum interactions. Their main drawbacks, however, are thefact that superconducting structures are very large and costly and havedifficulty in scaling to quantum processor sizes of thousands ormillions of quantum-bits (qubits). Furthermore, they need to operate atfew tens of milli-kelvin (mK) temperatures, that are difficult toachieve and where it is difficult to dissipate significant power tooperate the quantum machine.

SUMMARY OF THE INVENTION

The present invention describes a controlled quantum shift register fortransporting particles from one quantum dot to another in a quantumstructure. The shift register incorporates a succession of qdots withtunneling paths and control gates. By applying the appropriate controlsignals to the control gates a particle or a split quantum state can bemade to travel along the quantum shift register. Quantum shift registersare used to transport particles and quantum states from one position toanother. To enable quantum operations and calculations, the particlesare moved to interaction qdots where they are in close enough proximityto interaction with each other. From there, they are moved away usingshift registers. Shift registers are also used in quantum interactiongates and quantum cores within a quantum processing unit. Once acalculation is performed in one core, the results may be transported toanother core using shift registers.

The shift register also includes ancillary double interaction where twopairs of quantum dots provide an ancillary function. One pair of quantumdots has some quantum state while the second pair is placed in theHadamard state. Applying appropriate control pulses to the quantumstructure replicates the quantum state of the first pair of quantum dotsin the second pair.

The shift register also provides bifurcation where an access path issplit into two or more paths. Depending on the control pulse signalsapplied, quantum dots are extended into multiple paths.

Control of the shift register is provided by electric control pulses. Anoptional auxiliary magnetic field provides additional control of theshift register.

This, additional, and/or other aspects and/or advantages of theembodiments of the present invention are set forth in the detaileddescription which follows; possibly inferable from the detaileddescription; and/or learnable by practice of the embodiments of thepresent invention.

There is thus provided in accordance with the invention, a quantum shiftregister, comprising a semiconductor substrate, a plurality of quantumwells fabricated on the semiconductor substrate forming a plurality ofquantum dots arranged in sequential fashion, an oxide layer fabricatedover the plurality of quantum wells, a plurality of substantiallyfloating gates fabricated over the oxide layer and at least partiallyoverlaying the plurality of quantum wells, each floating gate operativeto provide conduction transport of a quantum particle between adjacentquantum wells via tunneling through the oxide layer, and a plurality ofcontrol gates electrostatically coupled to the plurality of floatinggates, whereby electric control gate pulses applied to the plurality ofcontrol gates control the floating gates between neighboring quantumdots such that one or more particles within the quantum dots aretransported from one quantum dot to another.

There is also provided in accordance with the invention, a quantum shiftregister, comprising a semiconductor substrate, a plurality of quantumwells fabricated on the semiconductor substrate forming a plurality ofquantum dots arranged in sequential fashion, an oxide layer fabricatedover the plurality of quantum wells, a plurality of substantiallyfloating gates fabricated over the oxide layer and at least partiallyoverlaying the plurality of quantum wells, each floating gate operativeto provide conduction transport of a quantum particle between adjacentquantum wells via tunneling through the oxide layer, a plurality ofcontrol gates electrostatically coupled to the plurality of floatinggates, whereby electric control gate pulses applied to the plurality ofcontrol gates control quantum tunneling paths between neighboringquantum dots such that one or more particles within the quantum dots aretransported from one quantum dot to another, and an auxiliary magneticfield covering at least the plurality of quantum dots and operative toprovide additional control on the plurality of quantum dots.

There is further provided in accordance with the invention, a quantumshift register method, comprising providing a semiconductor substrate,fabricating a plurality of quantum wells on the semiconductor substrateto form a plurality of quantum dots arranged in sequential fashion,fabricating an oxide layer over the plurality of quantum wells,fabricating a plurality of substantially floating gates over the oxidelayer and at least partially overlaying the plurality of quantum wells,each floating gate operative to provide conduction transport of aquantum particle between adjacent quantum wells via tunneling throughthe oxide layer, and fabricating a plurality of control gates, theplurality of control gates electrostatically coupled to the plurality offloating gates, whereby electric control gate pulses applied to theplurality of control gates control the floating gates betweenneighboring quantum dots such that one or more particles within thequantum dots are transported from one quantum dot to another.

There is also provided in accordance with the invention, a quantum shiftregister, comprising a semiconductor substrate, a plurality ofsemiconductor fins fabricated on the semiconductor substrate, oxidefabricated over the plurality of semiconductor fins, a plurality offloating gates, each floating gate at least partially overlapping a pairof neighboring semiconductor fins to form a plurality of quantum dotsarranged sequentially, each floating gate operative to provideconduction transport of a quantum particle between adjacent quantum dotsvia tunneling through the oxide layer, a plurality of control gateselectrostatically coupled to the plurality of floating gates, wherebyelectric control gate pulses applied to the plurality of control gatescontrol the floating gates between neighboring semiconductor fins suchthat one or more particles within the quantum dots are transported fromone quantum dot to another.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a high level block diagram illustrating a first examplequantum computer system constructed in accordance with the presentinvention;

FIG. 2 is a diagram illustrating an example quantum processing unitincorporating a plurality of DAC circuits;

FIG. 3 is a diagram illustrating an example quantum core incorporatingone or more quantum circuits;

FIG. 4 is a diagram illustrating a timing diagram of n example reset,injector, imposer, and detection control signals;

FIG. 5A is a diagram illustrating an example Bloch sphere;

FIG. 5B is a diagram illustrating an example θ angle control circuit;

FIG. 5C is a diagram illustrating an example θ angle control and φ anglecontrol circuits;

FIG. 5D is a diagram illustrating a Bloch sphere with no precession in apure state;

FIG. 5E is a diagram illustrating a Bloch sphere with precession in asuperposition state;

FIG. 5F is a diagram illustrating a Bloch sphere with combined θ and φangle rotation;

FIG. 6A is a diagram illustrating an example qubit with θ=0 anglecontrol;

FIG. 6B is a diagram illustrating an example qubit with θ<90 anglecontrol;

FIG. 6C is a diagram illustrating an example qubit with θ=180 anglecontrol;

FIG. 6D is a diagram illustrating an example qubit with ∂>180 anglecontrol;

FIG. 7A is a diagram illustrating an example qubit with θ=90 anglecontrol;

FIG. 7B is a diagram illustrating an example qubit with θ<90 anglecontrol;

FIG. 7C is a diagram illustrating an example qubit with θ>90 anglecontrol;

FIG. 7D is a diagram illustrating an example qubit with θ=180 anglecontrol;

FIG. 8A is a diagram illustrating an example pulsed Hadamard gate;

FIG. 8B is a diagram illustrating an example pulsed NOT gate;

FIG. 8C is a diagram illustrating an example pulsed rotation gate;

FIG. 8D is a diagram illustrating an example pulsed repeater gate;

FIG. 9A is a diagram illustrating a target semiconductor quantum gatewith electric field control;

FIG. 9B is a diagram illustrating a target semiconductor quantum gatewith electric and magnetic field control;

FIG. 9C is a diagram illustrating a target semiconductor quantum gatewith multiple electric field control;

FIG. 9D is a diagram illustrating a target semiconductor quantum gatewith multiple electric and multiple magnetic field control;

FIG. 10A is a diagram illustrating a target semiconductor quantum gatewith classic electronic control;

FIG. 10B is a diagram illustrating a target semiconductor quantum gatewith quantum control;

FIG. 10C is a diagram illustrating a target semiconductor quantum gatewith both classic electronic control and quantum control;

FIG. 11A is a diagram illustrating an example qubit with classicelectronic control;

FIG. 11B is a diagram illustrating an example qubit with both classicelectronic control and quantum control;

FIG. 11C is a diagram illustrating an example qubit having quantumcontrol with the control carrier at a close distance;

FIG. 11D is a diagram illustrating an example qubit having quantumcontrol with the control carrier at a far distance;

FIG. 12A is a diagram illustrating an example position based quantumsystem with θ angle and φ angle electric field control;

FIG. 12B is a diagram illustrating an example position based quantumsystem with θ angle electric field control and φ angle magnetic fieldcontrol;

FIG. 12C is a diagram illustrating an example position based quantumsystem with θ angle magnetic field control and φ angle electric fieldcontrol;

FIG. 12D is a diagram illustrating an example position based quantumsystem with θ angle electric field control and no φ angle externalcontrol;

FIG. 12E is a diagram illustrating an example quantum interaction gatewith electric field main control and magnetic field auxiliary control;

FIG. 12F is a diagram illustrating an example quantum interaction gatewith electric field main control and local and global magnetic fieldauxiliary control;

FIG. 12G is a diagram illustrating an example quantum interaction gatewith local magnetic field control; and

FIG. 12H is a diagram illustrating an example quantum interaction gatewith global magnetic field control and a plurality of local magneticfields control.

FIG. 13A is a diagram illustrating an example quantum processing unitincorporating a plurality of individual control signal DACs;

FIG. 13B is a diagram illustrating an example quantum processing unitincorporating shared control signal DACs;

FIG. 14A is a diagram illustrating an example quantum processing unitincorporating a combined amplitude and timing circuit;

FIG. 14B is a diagram illustrating an example quantum processing unitincorporating separate amplitude and timing circuits;

FIG. 15A is a diagram illustrating a first example control gate signal;

FIG. 15B is a diagram illustrating a second example control gate signal;

FIG. 15C is a diagram illustrating a third example control gate signal;

FIG. 15D is a diagram illustrating a fourth example control gate signal;

FIG. 15E is a diagram illustrating a fifth example control gate signal;

FIG. 15F is a diagram illustrating a sixth example control gate signal;

FIG. 15G is a diagram illustrating a seventh example control gatesignal;

FIG. 15H is a diagram illustrating an eighth example control gatesignal;

FIG. 15I is a diagram illustrating a ninth example control gate signal;

FIG. 15J is a diagram illustrating a tenth example control gate signal;

FIG. 15K is a diagram illustrating an eleventh example control gatesignal;

FIG. 15L is a diagram illustrating a twelfth example control gatesignal;

FIG. 15M is a diagram illustrating a thirteenth example control gatesignal;

FIG. 15N is a diagram illustrating a fourteenth example control gatesignal;

FIG. 15O is a diagram illustrating a fifteenth example control gatesignal;

FIG. 15P is a diagram illustrating a sixteenth example control gatesignal;

FIG. 15Q is a diagram illustrating a seventeenth example control gatesignal;

FIG. 15R is a diagram illustrating an eighteenth example control gatesignal;

FIG. 16A is a diagram illustrating a first example pair of control gatesignals G_(A) and G_(B);

FIG. 16B is a diagram illustrating a second example pair of control gatesignals G_(A) and G_(B);

FIG. 16C is a diagram illustrating a third example pair of control gatesignals G_(A) and G_(B);

FIG. 16D is a diagram illustrating a fourth example pair of control gatesignals G_(A) and G_(B);

FIG. 16E is a diagram illustrating a fifth example pair of control gatesignals G_(A) and G_(B);

FIG. 16F is a diagram illustrating a sixth example pair of control gatesignals G_(A) and G_(B);

FIG. 16G is a diagram illustrating a seventh example pair of controlgate signals G_(A) and G_(B);

FIG. 16H is a diagram illustrating an eighth example pair of controlgate signals G_(A) and G_(B);

FIG. 16I is a diagram illustrating a ninth example pair of control gatesignals G_(A) and G_(B);

FIG. 17A is a diagram illustrating an example quantum processing unitwith separate amplitude and time position control units;

FIG. 17B is a diagram illustrating an example quantum processing unitwith separate amplitude and time position control units and controladjustments for qubit entanglement;

FIG. 18A is a diagram illustrating a first example qubit with φ anglecontrol;

FIG. 18B is a diagram illustrating a second example qubit with φ anglecontrol;

FIG. 18C is a diagram illustrating a third example qubit with φ anglecontrol;

FIG. 18D is a diagram illustrating an example pair of qubits with φangle control;

FIG. 19A is a diagram illustrating an example planar and 3D quantum wellstructure fabricated using bulk semiconductor processes;

FIG. 19B is a diagram illustrating an example planar and 3D quantum wellstructure fabricated using silicon on insulator (SOI) semiconductorprocesses;

FIG. 19C is a diagram illustrating an example planar and 3D quantum wellstructure fabricated using bulk semiconductor processes and potentialdriven electrically;

FIG. 19D is a diagram illustrating an example planar and 3D quantum wellstructure fabricated using silicon on insulator (SOI) semiconductorprocesses and floating potential dependent on quantum particles;

FIG. 19E is a diagram illustrating example imposing on the potential ofa floating planar quantum well using an electrically driven adjacentlayer;

FIG. 19F is a diagram illustrating example imposing on the potential ofa floating planar quantum well using a floating layers with quantumparticles;

FIG. 19G is a diagram illustrating example imposing on the potential ofa floating 3D quantum well using an electrically driven adjacent layer;

FIG. 19H is a diagram illustrating example imposing on the potential ofa floating 3D quantum well using a floating layers with quantumparticles;

FIG. 20A is a diagram illustrating initialization of an examplecontrolled semiconductor shift register;

FIG. 20B is a diagram illustrating quantum superposition state of anexample controlled semiconductor shift register;

FIG. 20C is a diagram illustrating shifting of a first component of anexample controlled semiconductor shift register;

FIG. 20D is a diagram illustrating shifting of a second component of anexample controlled semiconductor shift register;

FIG. 21A is a diagram illustrating an example of linear, zig-zag, andangled controlled quantum shift registers with qubits using tunnelingthrough oxide layer and planar semiconductor process;

FIG. 21B is a diagram illustrating an example of linear, zig-zag, andangled controlled quantum shift registers with qubits using tunnelingthrough local depleted region in a well and planar semiconductorprocess;

FIG. 21C is a diagram illustrating an example of linear, zig-zag, andangled controlled quantum shift registers with qubits using tunnelingthrough oxide layer and 3D semiconductor process;

FIG. 21D is a diagram illustrating an example of linear, zig-zag, andangled controlled quantum shift registers with qubits using tunnelingthrough local depleted region in a fin and 3D semiconductor process;

FIG. 22 is a diagram illustrating an example quantum shift registerinterconnecting quantum interaction gates;

FIG. 23A is a diagram illustrating an example double V quantum structureincorporating quantum shift registers;

FIG. 23B is a diagram illustrating an example triple V quantum structureincorporating quantum shift registers;

FIG. 23C is a diagram illustrating an example H interaction quantum flowpath incorporating quantum shift registers;

FIG. 24 is a diagram illustrating example linear and zig-zag controlledquantum shift registers using tunneling through separate oxide layer;

FIG. 25 is a diagram illustrating an example z shift register in planarsemiconductor process using partial overlap of semiconductor well andcontrol gate;

FIG. 26 is a diagram illustrating an example quantum shift registerusing qdots realized in a continuous well with local depletion andvoltage driven imposing;

FIG. 27 is a diagram illustrating an example controlled quantum shiftregister with auxiliary magnetic field control;

FIG. 28A is a diagram illustrating an example quantum shift registerfabricated using planar semiconductor process using qubits withtunneling through separate layers;

FIG. 28B is a diagram illustrating an example quantum shift registerfabricated using planar semiconductor process using qubits withtunneling through local depleted wells;

FIG. 28C is a diagram illustrating an example quantum shift registerfabricated using 3D semiconductor process using qubits with tunnelingthrough separate layers;

FIG. 28D is a diagram illustrating an example quantum shift registerfabricated using 3D semiconductor process using qubits with tunnelingthrough local depleted wells;

FIG. 29A is a diagram illustrating a first example double interactionquantum structure;

FIG. 29B is a diagram illustrating a second example double interactionquantum structure;

FIG. 29C is a diagram illustrating a third example double interactionquantum structure;

FIG. 29D is a diagram illustrating a fourth example double interactionquantum structure;

FIG. 30 is a diagram illustrating an example double V structureincorporating double interaction quantum shift register;

FIG. 31 is a diagram illustrating an example double V structureincorporating double interaction quantum shift register and auxiliarymagnetic field control;

FIG. 32 is a diagram illustrating an example double V quantum structurewith interaction qdots and shifting qdots;

FIG. 33 is a diagram illustrating an example double interaction quantumstructure;

FIG. 34A is a diagram illustrating an example double interaction quantumstructure with planar semiconductor process using tunneling throughoxide;

FIG. 34B is a diagram illustrating an example double interaction quantumstructure with planar semiconductor process using tunneling throughlocal depletion region;

FIG. 35 is a diagram illustrating an example quantum interaction gatewith double interaction and interface devices on either end;

FIG. 36A is a diagram illustrating an example controlled quantum shiftregister incorporating ancillary gate;

FIG. 36B is a diagram illustrating an example controlled quantum shiftregister with Hadamard of the ancillary register;

FIG. 36C is a diagram illustrating an example controlled quantum shiftregister with loading of the main state;

FIG. 36D is a diagram illustrating an example controlled quantum shiftregister performing the ancillary operation;

FIG. 37A is a diagram illustrating an example quantum structure withdouble interaction using planar semiconductor qdots with tunnelingthrough oxide layer;

FIG. 37B is a diagram illustrating an example quantum structure withdouble interaction using planar semiconductor qdots with tunnelingthrough local depletion region;

FIG. 37C is a diagram illustrating an example quantum structure withdouble interaction using 3D semiconductor qdots with tunneling throughoxide layer;

FIG. 37D is a diagram illustrating an example quantum structure withdouble interaction using 3D semiconductor qdots with tunneling throughlocal depletion region;

FIG. 38A is a diagram illustrating an example quantum bifurcation gateusing planar semiconductor qdots with tunneling through oxide layer andpotential imposing on the qdot well;

FIG. 38B is a diagram illustrating an example quantum bifurcation gateusing planar semiconductor qdots with tunneling through local depletionregion induced by overlapping control gate;

FIG. 38C is a diagram illustrating an example quantum bifurcation gateusing 3D semiconductor qdots with tunneling through oxide layer andpotential imposing on the qdot well (or tunneling path);

FIG. 38D is a diagram illustrating an example quantum bifurcation gateusing 3D semiconductor qdots with tunneling through local depletionregion induced by an overlapping control gate;

FIG. 39 is a diagram illustrating an example grid based matrix or fabricquantum computation unit using quantum path merger and/or bifurcationimplemented with a shared qdot and shared tunneling path;

FIG. 40 is a diagram illustrating an example reconfigurable quantumcomputing unit using memory based reconfiguration control for bothreconfigurable access control and reconfigurable operation;

FIG. 41 is a diagram illustrating example quantum computing pathsincorporating multiple merger and bifurcations;

FIG. 42 is a diagram illustrating an example quantum computation pathbifurcation and/or merger using a shared access path and indirectpotential imposing on the quantum wells to determine thebifurcation/merger function;

FIG. 43 is a diagram illustrating an example quantum computation pathbifurcation and/or merging using planar semiconductor qdots withtunneling through oxide layer;

FIG. 44 is a diagram illustrating an example quantum computation pathbifurcation and/or merging using planar semiconductor qdots withtunneling through an oxide layer using shared quantum well with multipleoverlapping gates;

FIG. 45A is a diagram illustrating a first example quantum computationpath bifurcation/merging using a continuous well that extends in morethan two directions;

FIG. 45B is a diagram illustrating a second example quantum computationpath bifurcation/merging using a continuous well that extends in morethan two directions;

FIG. 46 is a diagram illustrating an example quantum computation pathwith both bifurcation and merging using a continuous well that extendsin more than two directions;

FIG. 47 is a diagram illustrating an example X shaped quantumcomputation path with bifurcation and/or merging using planarsemiconductor qdots with tunneling through oxide layer and a commontunneling path shared by multiple quantum wells;

FIG. 48 is a diagram illustrating an example X shaped quantumcomputation path with bifurcation and/or merging using planarsemiconductor qdots with tunneling through oxide layer and a common wellshared by multiple tunneling paths;

FIG. 49 is a diagram illustrating an example X shaped quantumcomputation path with bifurcation and/or merging using planarsemiconductor qdots with tunneling through local depletion region and acommon well shared by multiple tunneling paths;

FIG. 50 is a diagram illustrating an example multiple X shaped quantumcomputation path with bifurcation and/or merging using planarsemiconductor qdots with tunneling through local depletion region and acommon well shared by multiple tunneling paths;

FIG. 51A is a diagram illustrating an example quantum computation pathwith bifurcation/merging using 3D semiconductor qdots and tunnelingthrough oxide layer and sharing tunneling path with potential imposingon the well where electrical control of the tunneling causes bifurcationto the upper path;

FIG. 51B is a diagram illustrating an example quantum computation pathwith bifurcation/merging using 3D semiconductor qdots and tunnelingthrough oxide layer and sharing tunneling path with potential imposingon the well where electrical control of the tunneling causes bifurcationto the lower path;

FIG. 52A is a diagram illustrating an example magnetically controlledquantum bifurcation gate using an inductor or resonator to create thecontrol magnetic field to cause tunneling to the upper path;

FIG. 52B is a diagram illustrating an example magnetically controlledquantum bifurcation gate using an inductor or resonator to create thecontrol magnetic field to cause tunneling to the lower path;

FIG. 53 is a diagram illustrating an example quantum computation pathwith bifurcation/merging using 3D semiconductor qdots and tunnelingthrough oxide layer and both shared tunneling path and sharedsemiconductor fin;

FIG. 54 is a diagram illustrating an example quantum computation pathwith bifurcation/merging using 3D semiconductor qdots and tunnelingthrough oxide layer and shared tunneling path with potential imposing onthe tunneling path;

FIG. 55 is a diagram illustrating an example quantum computation pathmerging/bifurcation gate using 3D semiconductor qdots with tunnelingthrough oxide layer;

FIG. 56 is a diagram illustrating an example quantum computation pathwith both merging/bifurcation using 3D semiconductor qdots withtunneling through local depletion region;

FIG. 57 is a diagram illustrating an example I shaped controlled quantumshift register with bidirectional flow;

FIG. 58 is a diagram illustrating an example multiple V controlledquantum shift register structure;

FIG. 59 is a diagram illustrating an example double V controlled quantumshift register in a resonator or inductor based magnetic field control;

FIG. 60 is a diagram illustrating an example double V controlled quantumshift register using planar semiconductor process with tunneling throughoxide layer;

FIG. 61 is a diagram illustrating an example controlled quantum shiftregister using planar semiconductor process with tunneling through localdepleted well;

FIG. 62 is a diagram illustrating an example controlled quantum shiftregister using planar semiconductor process with tunneling through oxidelayer;

FIG. 63 is a diagram illustrating an example controlled quantum shiftregister using 3D semiconductor process with tunneling through localdepleted well; and

FIG. 64 is a diagram illustrating an example controlled quantum shiftregister using 3D semiconductor process with tunneling through oxidelayer.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention. Itwill be understood by those skilled in the art, however, that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingfigures. Detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention which are intended to beillustrative, and not restrictive.

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings.

The figures constitute a part of this specification and includeillustrative embodiments of the present invention and illustrate variousobjects and features thereof. Further, the figures are not necessarilyto scale, some features may be exaggerated to show details of particularcomponents. In addition, any measurements, specifications and the likeshown in the figures are intended to be illustrative, and notrestrictive. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention. Further, where considered appropriate,reference numerals may be repeated among the figures to indicatecorresponding or analogous elements.

Because the illustrated embodiments of the present invention may for themost part, be implemented using electronic components and circuits knownto those skilled in the art, details will not be explained in anygreater extent than that considered necessary, for the understanding andappreciation of the underlying concepts of the present invention and inorder not to obfuscate or distract from the teachings of the presentinvention.

Any reference in the specification to a method should be applied mutatismutandis to a system capable of executing the method. Any reference inthe specification to a system should be applied mutatis mutandis to amethod that may be executed by the system.

Throughout the specification and claims, the following terms take themeanings explicitly associated herein, unless the context clearlydictates otherwise. The phrases “in one embodiment,” “in an exampleembodiment,” and “in some embodiments” as used herein do not necessarilyrefer to the same embodiment(s), though it may. Furthermore, the phrases“in another embodiment,” “in an alternative embodiment,” and “in someother embodiments” as used herein do not necessarily refer to adifferent embodiment, although it may. Thus, as described below, variousembodiments of the invention may be readily combined, without departingfrom the scope or spirit of the invention.

In addition, as used herein, the term “or” is an inclusive “or”operator, and is equivalent to the term “and/or,” unless the contextclearly dictates otherwise. The term “based on” is not exclusive andallows for being based on additional factors not described, unless thecontext clearly dictates otherwise. In addition, throughout thespecification, the meaning of “a,” “an,” and “the” include pluralreferences. The meaning of “in” includes “in” and “on.”

The following definitions apply throughout this document.

A quantum particle is defined as any atomic or subatomic particlesuitable for use in achieving the controllable quantum effect. Examplesinclude electrons, holes, ions, photons, atoms, molecules, artificialatoms. A carrier is defined as an electron or a hole in the case ofsemiconductor electrostatic qubit. Note that a particle may be split andpresent in multiple quantum dots. Thus, a reference to a particle alsoincludes split particles.

In quantum computing, the qubit is the basic unit of quantuminformation, i.e. the quantum version of the classical binary bitphysically realized with a two-state device. A qubit is a two statequantum mechanical system in which the states can be in a superposition.Examples include (1) the spin of the particle (e.g., electron, hole) inwhich the two levels can be taken as spin up and spin down; (2) thepolarization of a single photon in which the two states can be taken tobe the vertical polarization and the horizontal polarization; and (3)the position of the particle (e.g., electron) in a structure of twoqdots, in which the two states correspond to the particle being in oneqdot or the other. In a classical system, a bit is in either one stateor the other. Quantum mechanics, however, allows the qubit to be in acoherent superposition of both states simultaneously, a propertyfundamental to quantum mechanics and quantum computing. Multiple qubitscan be further entangled with each other.

A quantum dot or qdot (also referred to in literature as QD) is ananometer-scale structure where the addition or removal of a particlechanges its properties is some ways. In one embodiment, quantum dots areconstructed in silicon semiconductor material having typical dimensionin nanometers. The position of a particle in a qdot can attain severalstates. Qdots are used to form qubits and qudits where multiple qubitsor qudits are used as a basis to implement quantum processors andcomputers.

A quantum interaction gate is defined as a basic quantum logic circuitoperating on a small number of qubits or qudits. They are the buildingblocks of quantum circuits, just like the classical logic gates are forconventional digital circuits.

A qubit or quantum bit is defined as a two state (two level) quantumstructure and is the basic unit of quantum information. A qudit isdefined as a d-state (d-level) quantum structure. A qubyte is acollection of eight qubits.

The terms control gate and control terminal are intended to refer to thesemiconductor structure fabricated over a continuous well with a localdepleted region and which divides the well into two or more qdots. Theseterms are not to be confused with quantum gates or classical FET gates.

Unlike most classical logic gates, quantum logic gates are reversible.It is possible, however, although cumbersome in practice, to performclassical computing using only reversible gates. For example, thereversible Toffoli gate can implement all Boolean functions, often atthe cost of having to use ancillary bits. The Toffoli gate has a directquantum equivalent, demonstrating that quantum circuits can perform alloperations performed by classical circuits.

A quantum well is defined as a low doped or undoped continuous depletedsemiconductor well that functions to contain quantum particles in aqubit or qudit. The quantum well may or may not have contacts and metalon top. A quantum well holds one free carrier at a time or at most a fewcarriers that can exhibit single carrier behavior.

A classic well is a medium or high doped semiconductor well contactedwith metal layers to other devices and usually has a large number offree carriers that behave in a collective way, sometimes denoted as a“sea of electrons.”

A quantum structure or circuit is a plurality of quantum interactiongates. A quantum computing core is a plurality of quantum structures. Aquantum computer is a circuit having one or more computing cores. Aquantum fabric is a collection of quantum structures, circuits, orinteraction gates arranged in a grid like matrix where any desiredsignal path can be configured by appropriate configuration of accesscontrol gates placed in access paths between qdots and structures thatmake up the fabric.

In one embodiment, qdots are fabricated in low doped or undopedcontinuous depleted semiconductor wells. Note that the term ‘continuous’as used herein is intended to mean a single fabricated well (even thoughthere could be structures on top of them, such as gates, that modulatethe local well's behavior) as well as a plurality of abutting contiguouswells fabricated separately or together, and in some cases mightapparently look as somewhat discontinuous when ‘drawn’ using a computeraided design (CAD) layout tool.

The term classic or conventional circuitry (as opposed to quantumstructures or circuits) is intended to denote conventional semiconductorcircuitry used to fabricate transistors (e.g., FET, CMOS, BIT, FinFET,etc.) and integrated circuits using processes well-known in the art.

The term Rabi oscillation is intended to denote the cyclic behavior of aquantum system either with or without the presence of an oscillatorydriving field. The cyclic behavior of a quantum system without thepresence of an oscillatory driving field is also referred to asoccupancy oscillation.

Throughout this document, a representation of the state of the quantumsystem in spherical coordinates includes two angles θ and φ. Consideringa unitary sphere, as the Hilbert space is a unitary state, the state ofthe system is completely described by the vector W. The vector W inspherical coordinates can be described in two angles θ and φ. The angleθ is between the vector W and the z-axis and the angle φ is the anglebetween the projection of the vector on the XY plane and the x-axis.Thus, any position on the sphere is described by these two angles θ andφ. Note that for one qubit angle θ representation is in threedimensions. For multiple qubits θ representation is in higher orderdimensions.

Quantum Computing System

A high-level block diagram illustrating a first example quantum computersystem constructed in accordance with the present invention is shown inFIG. 1. The quantum computer, generally referenced 10, comprises aconventional (i.e. not a quantum circuit) external support unit 12,software unit 20, cryostat unit 36, quantum processing unit 38, clockgeneration units 33, 35, and one or more communication busses betweenthe blocks. The external support unit 12 comprises operating system (OS)18 coupled to communication network 76 such as LAN, WAN, PAN, etc.,decision logic 16, and calibration block 14. Software unit 20 comprisescontrol block 22 and digital signal processor (DSP) 24 blocks incommunication with the OS 18, calibration engine/data block 26, andapplication programming interface (API) 28.

Quantum processing unit 38 comprises a plurality of quantum corecircuits 60, high speed interface 58, detectors/samplers/output buffers62, quantum error correction (QEC) 64, digital block 66, analog block68, correlated data sampler (CDS) 70 coupled to one or more analog todigital converters (ADCs) 74 as well as one or more digital to analogconverters (DACs, not shown), clock/divider/pulse generator circuit 42coupled to the output of clock generator 35 which comprises highfrequency (HF) generator 34. The quantum processing unit 38 furthercomprises serial peripheral interface (SPI) low speed interface 44,cryostat software block 46, microcode 48, command decoder 50, softwarestack 52, memory 54, and pattern generator 56. The clock generator 33comprises low frequency (LF) generator 30 and power amplifier (PA) 32,the output of which is input to the quantum processing unit (QPU) 38.Clock generator 33 also functions to aid in controlling the spin of thequantum particles in the quantum cores 60.

The cryostat unit 36 is the mechanical system that cools the QPU down tocryogenic temperatures. Typically, it is made from metal and it can befashioned to function as a cavity resonator 72. It is controlled bycooling unit control 40 via the external support unit 12. The coolingunit control 40 functions to set and regulate the temperature of thecryostat unit 36. By configuring the metal cavity appropriately, it ismade to resonate at a desired frequency. A clock is then driven via apower amplifier which is used to drive the resonator which creates amagnetic field. This magnetic field can function as an auxiliarymagnetic field to aid in controlling one or more quantum structures inthe quantum core.

The external support unit/software units may comprise any suitablecomputing device or platform such as an FPGA/SoC board. In oneembodiment, it comprises one or more general purpose CPU cores andoptionally one or more special purpose cores (e.g., DSP core, floatingpoint, etc.) that that interact with the software stack that drives thehardware, i.e. the QPU. The one or more general purpose cores executegeneral purpose opcodes while the special purpose cores executefunctions specific to their purpose. Main memory comprises dynamicrandom access memory (DRAM) or extended data out (EDO) memory, or othertypes of memory such as ROM, static RAM, flash, and non-volatile staticrandom access memory (NVSRAM), bubble memory, etc. The OS may compriseany suitable OS capable of running on the external support unit andsoftware units, e.g., Windows, MacOS, Linux, QNX, NetBSD, etc. Thesoftware stack includes the API, the calibration and management of thedata, and all the necessary controls to operate the external supportunit itself.

The clock generated by the high frequency clock generator 35 is input tothe clock divider 42 that functions to generate the signals that drivethe QPU. Low frequency clock signals are also input to and used by theQPU. A slow serial/parallel interface (SPI) 44 functions to handle thecontrol signals to configure the quantum operation in the QPU. The highspeed interface 58 is used to pump data from the classic computer, i.e.the external support unit, to the QPU. The data that the QPU operates onis provided by the external support unit.

Non-volatile memory may include various removable/non-removable,volatile/nonvolatile computer storage media, such as hard disk drivesthat reads from or writes to non-removable, nonvolatile magnetic media,a magnetic disk drive that reads from or writes to a removable,nonvolatile magnetic disk, an optical disk drive that reads from orwrites to a removable, nonvolatile optical disk such as a CD ROM orother optical media. Other removable/non-removable, volatile/nonvolatilecomputer storage media that can be used in the exemplary operatingenvironment include, but are not limited to, magnetic tape cassettes,flash memory cards, digital versatile disks, digital video tape, solidstate RAM, solid state ROM, and the like.

The computer may operate in a networked environment via connections toone or more remote computers. The remote computer may comprise apersonal computer (PC), server, router, network PC, peer device or othercommon network node, or another quantum computer, and typically includesmany or all of the elements described supra. Such networkingenvironments are commonplace in offices, enterprise-wide computernetworks, intranets and the Internet.

When used in a LAN networking environment, the computer is connected tothe LAN via network interface 76. When used in a WAN networkingenvironment, the computer includes a modem or other means forestablishing communications over the WAN, such as the Internet. Themodem, which may be internal or external, is connected to the system busvia user input interface, or other appropriate mechanism.

Computer program code for carrying out operations of the presentinvention may be written in any combination of one or more programminglanguages, including an object oriented programming language such asJava, Smalltalk, C++, C# or the like, conventional proceduralprogramming languages, such as the “C” programming language, andfunctional programming languages such as Python, Hotlab, Prolog andLisp, machine code, assembler or any other suitable programminglanguages.

Also shown in FIG. 1 is the optional data feedback loop between thequantum processing unit 38 and the external support unit 12 provided bythe partial quantum data read out. The quantum state is stored in thequbits of the one or more quantum cores 60. The detectors 62 function tomeasure/collapse/detect some of the qubits and provide a measured signalthrough appropriate buffering to the output ADC block 74. The resultingdigitized signal is sent to the decision logic block 16 of the externalsupport unit 12 which functions to reinject the read out data back intothe quantum state through the high speed interface 58 and quantuminitialization circuits. In an alternative embodiment, the output of theADC is fed back to the input of the QPU.

In one embodiment, quantum error correction (QEC) is performed via QECblock 64 to ensure no errors corrupt the read out data that isreinjected into the overall quantum state. Errors may occur in quantumcircuits due to noise or inaccuracies similarly to classic circuits.Periodic partial reading of the quantum state function to refresh allthe qubits in time such that they maintain their accuracy for relativelylong time intervals and allow the complex computations required by aquantum computing machine.

It is appreciated that the architecture disclosed herein can beimplemented in numerous types of quantum computing machines. Examplesinclude semiconductor quantum computers, superconducting quantumcomputers, magnetic resonance quantum computers, optical quantumcomputers, etc. Further, the qubits used by the quantum computers canhave any nature, including charge qubits, spin qubits, hybridspin-charge qubits, etc.

In one embodiment, the quantum structure disclosed herein is operativeto process a single particle at a time. In this case, the particle canbe in a state of quantum superposition, i.e. distributed between two ormore locations or charge qdots. In an alternative embodiment, thequantum structure processes two or more particles at the same time thathave related spins. In such a structure, the entanglement between two ormore particles could be realized. Complex quantum computations can berealized with such a quantum interaction gate/structure or circuit.

In alternative embodiments, the quantum structure processes (1) two ormore particles at the same time having opposite spin, or (2) two or moreparticles having opposite spins but in different or alternate operationcycles at different times. In the latter embodiment, detection isperformed for each spin type separately.

A diagram illustrating an example quantum processing unit incorporatinga plurality of DAC circuits is shown in FIG. 2. The quantum processingunit, generally referenced 100, comprises interface and digital controlunit (DSP) 106, quantum control/mixed signal and analog control block108 having a plurality of DACs 112, and quantum interaction gate,circuit, or core 110 including reset circuits 114, injector circuits116, imposer circuits 118, and detector circuits 120. The quantumprocessing unit is operative to receive control information from theexternal support unit 104 which is in communication with a usercomputing device 102 typically comprising a classic computer.

Note that the digital control unit 106 combined with the mixed signaland analog control circuit 108 provide a reprogrammable capability tothe quantum interaction gates/circuits/cores 110. Thus, using the samephysical structure realized in the circuitry different types of quantumoperations can be achieved by changing the electronic control signalsgenerated by the DACs 112. The quantum processing unit 100 can beappropriately programmed via software to realize numerous quantumoperations depending on the particular application, similar to softwarethat controls classic computers where a software stack determinesmultiple functionality operation of the computer circuit.

In one embodiment, the reset, injector, imposer, and detector circuitsof the quantum interaction gate/circuit/core are controlled by analogsignals generated by a plurality of digital to analog converters (DACs)112. The digital command data that feed the DACs are generated by thequantum control/mixed signal and analog control circuit 108 inaccordance with commands received from the external support unit 104which are interpreted and processed by the I/F and digital control unit106.

A diagram illustrating an example quantum core incorporating one or morequantum circuits is shown in FIG. 3. The quantum core, generallyreferenced 130, comprises one or more quantum circuits 140 eachcomprising one or more quantum wells 142. Each quantum circuit hascorresponding reset circuitry 134, injector circuitry 136, imposercircuitry 132, and detector circuitry 138 that together electronicallycontrol the operation of the semiconductor quantum circuit.

A diagram illustrating a timing diagram of example reset, injector,imposer, and detection control signals is shown in FIG. 4. As describedsupra, the quantum circuits generally require reset, injecting,imposing, and detecting control signals to achieve the desired quantumoperation. In one embodiment, the reset control signal 150 comprises avariable pulse that is between 1 and 100 microseconds. The reset pulseis followed by the injector pulse 152 that is typically operative toinject a single particle into the quantum circuit. One or more imposerpulses 154, 156 functions to move the particle to and from interactionqdots. Detector reference sampling pulse 158, detector signal samplingpulse 160, and detector output pulse 162 function to control thedetection process that determines the presence or absence of a particleat the output of the quantum circuit.

A diagram illustrating an example Bloch sphere is shown in FIG. 5A. Inquantum mechanics, the Bloch sphere 170 is a geometrical representationof the pure state of a two-level quantum system or qubit. The space ofpure states of a quantum system is given by the one-dimensionalsubspaces of the corresponding Hilbert space. The north and south polesof the sphere correspond to the pure states of the system, e.g., |0> or|A> and |1> or |B>, whereas the other points on the sphere correspond tothe mixed states. The Hilbert space is the mathematical space whereoperations are performed in the system. In general, the system can bedescribed graphically by a vector in the x, y, z spherical coordinates.A representation of the state of the system in spherical coordinatesincludes two angles θ and φ. Considering a unitary sphere, as theHilbert space is a unitary state, the state of the system is completelydescribed by the vector W. The vector W in spherical coordinates can bedescribed in two angles θ and φ. The angle θ is between the vector W andthe z-axis and the angle φ is the angle between the projection of thevector on the XY plane and the x-axis. Thus, any position on the sphereis described by these two angles θ and φ.

Note that to represent a multi-dimensional Hilbert space of a quantumsystem of two or more qubits, a graphical representation can no longerbe used as four or more dimensions are difficult to visualizegraphically. The precise position or the precise state in the Hilbertspace cannot be determined. Consider the Heisenberg uncertainty lawwhich states that you cannot know for sure both the position and thespin (or momentum) of an electron or a carrier. Thus, both the positionand the spin of the electron cannot be determined simultaneously. Eitherthe position can be known separately or the spin separately, but bothcannot be known at the same time. Fundamentally, this means that thereis no complete observability of a quantum system.

Consider a quantum structure that has two or more qdots such as shown inFIG. 6A. The qubit 192 comprises two qdots 193 D_(A) and D_(B), acontrol terminal 191, and depleted tunneling path 195. The qubit, whichcan be implemented using any kind of technology, planar, 3D, etc., alsocomprises an injector (not shown) and a detector (not shown) and anattempt is made to detect whether an electron (or a hole) is present ornot. The quantum superposition space is created by superposing two basestates. There is one state which means that the electron is present inthe left qdot and there is another state where the electron is presentin the right qdot.

Note that whenever the quantum state is detected, the entire complexfunctionality or description of a quantum state cannot be measured. Onlythe projection of the W vector on the |0> and |1> points of the z-axiscan be determined. Thus, a measurement means projecting the W vectoronto the z-axis, which is the axis of the pure states or the base statesof the quantum system.

The electron can be present on the left qdot D_(A) or it can be presentin the right qdot D_(B). By adjusting the control voltage 198 providedby control pulse generator V₁ 194 applied to the control terminal, thetunneling barrier is modulated. If the barrier is high (at the timeindicator line 190) then the electron will be locked into a givenposition, for example, in the left qdot D_(A) as indicated by theelectron probability graph showing a probability of one for the electronto be in qdot D_(A). The corresponding Bloch sphere 197 is also shownrepresenting the electron 196 in the base state |A> for θ=0 degrees.

As shown in FIG. 6B, as the tunneling barrier of the qubit 202 islowered via the control voltage 208 provided by control pulse generatorV₁ 204, the electron starts tunneling. Lowering the tunnel barriercauses the electron to start moving from the left qdot to the rightqdot. The corresponding Bloch sphere 209 is also shown representing theelectron 206/207 in a split quantum state for θ<90 degrees. How much andhow fast the electron moves depends on the qubit geometry and twoparameters of the control signal that controls the control terminal:amplitude and pulse width. In this example, a lower amplitudecorresponds to a larger decrease of the tunnel barrier and the electronwill tunnel faster. This means that it will go from one side to anotherfaster. This also means that the Rabi oscillation frequency will behigher. If the voltage is such that the tunnel barrier is not that low,in a moderate position, then the tunneling current between the two qdotswill be lower and the electron will travel slower. The Rabi oscillationfrequency is also lower, depending on the amplitude. Thus, how much theelectron travels from one qdot to the other depends on the height of thetunnel barrier. If the tunnel barrier is lowered only a little bit, thenonly a little bit of the electron will tunnel to the other side withinan allotted time. Given enough time, more electrons will tunnel to theother side and if the port is wide, the entire electron will go to theother side, i.e. to D_(B). Thus, the amount of splitting of theelectrons between the two qdots depends both on the amplitude and on thepulse width. The invention provides a semiconductor quantum structurecomprising an electronic control that controls the amplitude and thepulse width of the control signal which determines exactly what happenswith the quantum state and the electron, i.e. how much it's wavefunctionwill be split between the two qdots.

Note that the electron tunnels only when the tunnel barrier is low. Whenthe tunnel barrier is high, the electron cannot tunnel and it stays inwhatever state it was left before the tunnel barrier was raised. If acontrol pulse is applied that is equal to the Rabi oscillation period,which is 2π, then the electron starts from the left side D_(A), tunnelsto D_(B) and will come back to D_(A). If a control pulse equal to π isapplied, i.e. half the Rabi oscillation, the electron will travel fromthe left side to the right side, as shown in FIG. 6C. If control pulseτ_(π) provided by control pulse generator V₁ 214 is applied to thecontrol terminal that lowers the tunnel barrier for half the Rabioscillation, the electron will go from the left side to the right sideof the qubit 212. Any other values uneven to the half-period will resultinto a splitting of the electron. The Bloch sphere 217 shows theelectron 216 in the base state |B> for θ=180 degrees as indicated by theelectron probability graph showing probability of one for the electron216 to be in qdot D_(B).

Note that the control described herein works both on full electrons,which are called pure states, as well as on split states. Considering aqubit 222 in a split state, as shown in FIG. 6D, e.g., 25% on the leftand 75% on the right, if a control pulse of τ_(π) provided by controlpulse generator V₁ 224 is applied to the control terminal, the electronin the two qdots will be split, i.e. 75% on the left and 25% on theright. The Bloch sphere representation 229 shows the electron 226/227 ina split state for θ>180 degrees. Thus, this type of control works notonly with separated full electrons, it works with any kind of splitelectron which means a quantum state.

The control can be applied to single qubits as well as multiple qubitsmaking up a quantum interaction gate, circuit or core. In this case, acontrol signal is supplied for each control terminal in the structure.And for each of those control signals, the amplitude and the pulse widthis controlled in a given fashion to create a given functionality for thequantum structure.

With reference to the Bloch sphere, whether the electron is in the leftor right qdot is determined by the θ angle which is the single anglethat can be detected externally, although sometimes multiplemeasurements might be needed. Thus, if one puts a detector on the D_(B)qdot in FIG. 6A, it can be detected that the electron is not present inthe D_(A) qdot. If the detector is placed on qdot D_(B) in FIG. 6C,presence of the electron will be detected. In the split case, the splitelectron is only a quantum description. Whenever it is detected, thestate collapses to a classic state. For example, considering FIG. 6B,qdot D_(A) is detected as a split electron where 75% of the time it isdetected, but whenever it is detected, an electron will be present ornot present. Performing a large number of measurements consecutively,75% of the time an electron will be present and 25% of the time it willnot be present. With a larger number of detections, the results convergetowards the probability split of the quantum state.

Regarding notation for the pure or base states, when the electron is inthe left side of the qubit, this is referred to as state 0 or A and itis represented by a vector that goes to the north pole as shown in FIG.5D in Bloch sphere 182. When the electron is in the right qdot, this isreferred to as state 1 or B and it is represented by a vector that goesto the south pole. By looking to the projection of a generalized quantumstate it can be concluded if the state is completing on the left side orcompleting on the right side, which would be either the 0 or 1 state, orif it is a superposed case, it can be determined what percentage is instate 0 and what percentage is in state 1. This is the projection of theW quantum vector onto the z-axis in the Bloch sphere.

Note that the angle φ cannot be directly measured. The φ angle comesfrom the full complex Hilbert description of the quantum state. And itis a representation of the ground state in the quantum system. Having aground state energy means that the energy level of the electron evolvesover time although the projection on the z-axis is the same.

The electron is in one of the pure states as shown in FIG. 5D either Aor B, 0 or 1 then the vector will stay fixed all the time. If theelectron is in a superposed position, i.e. a percentage in state A and apercentage in state B, this means that the vector will be inclined at anangle as shown in FIG. 5E. In this case, what happens in time is thestate in the Bloch sphere 184 will have a procession which is a rotationaround the z-axis. The projection of the vector W on the z-axis is thesame all the time so the electron for example is split in a given way.From the quantum representation in the Bloch sphere, however, it isrotated around the state which means that the angle φ varies in time.

Consider starting from the state shown in FIG. 5E where the angle isrotated and it is desired to move to a different angle, which is theangle θ shown in FIG. 5F. What does not happen is that the electronsimply jumps from one state to the other. Rather, the timerepresentation of the state evolves over time which changes both theangle θ and the angle φ. This is represented on the Bloch sphere 186 asa spiral. Starting from the state in FIG. 5E, the electron proceeds toprocession about the z-axis but at the same time the θ angle changes.The particle travels around the z-axis several times on a processionuntil arriving in the final desired state.

Similarly, this is what happens in the quantum interaction structuresdescribed herein. Applying a control signal to the control terminal, theelectron splits meaning that the electron will go from one θ angle toanother but at the same time performs a procession around the z-axis.The invention provides a quantum system with a means of controlling justthe θ angles which from a position or a charge qubit is sufficient ifthe location of the electron is known. FIG. 5B shows a quantum system174 with θ angle control 172 only. In this case, the φ angle isunimportant.

Alternatively, a quantum system is provided where both the θ and φangles are controlled. This is shown in FIG. 5C which includes quantumsystem 180 with θ angle control 176 as well as φ angle control 178. Notethat considering a single qubit, the φ angle typically is not criticalbecause detection of a single electron yields the same resultsundifferentiated with respect to φ. The projection on the z-axis of thestate vector with angle θ will always be the same regardless of whereexactly in the procession the electron is. This is not the case,however, with a two or more qubit state. In this case, the φ angles ofeach of the states matter. The absolute value angle φ cannot be known ormeasured, but for two qubits, for example, the difference between φ1 andφ2 is important because it impacts the projection on the z-axis andtherefore the final result. Thus, either the angle θ can be controlledor both θ and φ can be controlled.

A diagram illustrating an example qubit with θ=90 degree angle controlis shown in FIG. 7A. The qubit 232 comprises a left qdot D_(A) and aright qdot D_(B) with control pulse generator V₁ 234 providing a controlsignal 238 to the control terminal. The Bloch sphere representation 231also shows the equal distribution state. As described supra, theelectron can be in other than a base state. There is a middle point whenthe electron is equally split between the two sides. It is appreciated,however, that the electron 236, 237 is present all the time in bothqdots or multiple qdots. It is only that the probability is split 50-50.When the electron is split 50-50 this is called a Hadamard gate resultwhich is widely used in quantum computing. The Hadamard gate takes anelectron and places it in an equal probability distribution. TheHadamard state is represented by a vector that is at 90 degrees. Sincethe Hadamard state is a split state, it also has a precession. The statetravels on the Bloch sphere 231 all the time. And the speed of travelingis the speed of precession which is dependent on the base energy level.The higher the tunnel barrier energy the higher the procession speed.The lower the energy the lower the precession speed.

For the Hadamard gate, the pulse width τ_(π/2) of the control signal 238applied is a quarter of the Rabi oscillation. With reference to FIGS.6A, 6B, 6C, and 6D, the control signal pulse that was half the Rabioscillation period was applied. Applying pulses that are half the Rabioscillation period causes the electron to go from one side to the other.Applying pulses that are a quarter of the Rabi oscillation, causes theelectron to pass through those states half-way and then stop. So forexample, after the first π/2 pulse the electron is split equally 50-50and is locked because the tunnel is stopped. This can then be used inthe quantum computation such as in calculating quantum error correction.

A diagram illustrating an example qubit state at the time instance 240is shown in FIG. 7B. The qubit 242 comprises a left qdot D_(A) and aright qdot D_(B) with control pulse generator V₁ 244 providing a controlsignal 248 to the control terminal. Since the tunnel barrier is stillhigh, the electron 246, 247 remains since the time instance 230 in theequal distribution state as indicated in the Bloch sphere 241.

A diagram illustrating an example qubit state at the time instance 250is shown in FIG. 7C. The qubit 252 comprises a left qdot D_(A) and aright qdot D_(B) with control pulse generator V₁ 254 providing a controlsignal 258 to the control terminal. Since the time instance 240, thetunnel barrier got lowered and so in this case, the probability for theelectron 256, 257 is split 15-85 as shown in the electron probabilitygraph and the Bloch sphere representation 251.

A diagram illustrating an example qubit state at time instance 260 isshown in FIG. 7D. The qubit 262 comprises a left qdot D_(A) and a rightqdot D_(B) with control pulse generator V₁ 264 providing a controlsignal 268 to the control terminal. The tunnel barrier was raised againafter the time instance 250 and so in this case, the electron 266 is inthe base state |B> as shown in the electron probability graph and theBloch sphere representation 261.

Several different types of quantum interaction gates will now bedescribed. A diagram illustrating an example pulsed Hadamard gate isshown in FIG. 8A. The Hadamard gate, generally referenced 270, asdescribed supra represents the 50-50 equal distribution quantum state.It is represented by the notation “H” 272. A control pulse has a pulsewidth of one quarter of the Rabi oscillation and places the gate intothe Hadamard state.

A diagram illustrating an example pulsed NOT gate is shown in FIG. 8B.The pulsed NOT gate, generally referenced 280, flips the initial basestate from |0> to |1> or vice versa. It is represented by the notation“NOT” 282. A control pulse having a pulse width of one half the Rabioscillation provides the pulsed NOT gate functionality.

A diagram illustrating an example pulsed rotation gate is shown in FIG.8C. The pulsed rotation gate, generally referenced 290, functions toapply a rotation to the initial state. It is represented by the notation“R” 292. A control pulse having a pulse width not exactly equal ton*T_(Rabi/4), where n is a positive integer, provides the pulsedrotation gate functionality.

A diagram illustrating an example pulsed repeater gate is shown in FIG.8D. The pulsed repeater gate, generally referenced 300, maintains theinitial state. It is represented by the notation “Rep” 302. A controlpulse having a pulse width equal to the Rabi oscillation provides thepulsed repeater gate functionality.

A target semiconductor quantum interaction gate is defined as thequantum interaction gate that is to be controlled. A quantum interactiongate is generally a quantum structure having several qubits, e.g., one,two, three, four, etc. A semiconductor quantum interaction gate can bejust a single qubit that can be controlled multiple ways. In oneembodiment, an electric field provides the control that is created, forexample, by a voltage applied to a control terminal. Note that there canbe multiple electric control fields. In this case, there are multiplecontrol terminals where different voltages are applied to each of them.In another embodiment, multiple quantum interaction gates can be usedwhere the control terminals are appropriately controlled to realizedifferent quantum functions.

A second way of controlling the quantum interaction gates is by using aninductor or resonator. In one embodiment, an electric field functions asthe main control and an auxiliary magnetic field provides additionalcontrol on the control gate. The magnetic field is used to controldifferent aspects of the quantum structure. The magnetic field has animpact on the spin of the electron such that the spin tends to align tothe magnetic field. This means that applying a magnetic field to acharge qubit quantum gate can determine the carriers, e.g., theelectrons, that are processed and what kind of spin orientation theyhave. Considering the position and the spin of the particle, both cannotbe determined but each can be determined one at a time. If the spin ofthe electron is changed, however, that also impacts its position. Inaddition, changing the position of an electron impacts the spin althoughit cannot be measured.

A diagram illustrating a target semiconductor quantum gate with electricfield control is shown in FIG. 9A. In one embodiment, electric fieldcontrol 312 is applied to the target semiconductor quantum gate 310.

A diagram illustrating a target semiconductor quantum gate with electricand magnetic field control is shown in FIG. 9B. In another embodiment,electric field control 332 as well as auxiliary magnetic field control334 are applied to the target semiconductor quantum gate 330.

A diagram illustrating a target semiconductor quantum gate with multipleelectric field control is shown in FIG. 9C. In another embodiment,multiple electric field controls 322 are applied to the targetsemiconductor quantum gate 320.

A diagram illustrating a target semiconductor quantum gate with multipleelectric and multiple magnetic field controls is shown in FIG. 9D. Inanother embodiment, multiple electric field controls 342 as well asmultiple auxiliary magnetic field controls 344 are applied to the targetsemiconductor quantum gate 340.

With reference to the target semiconductor quantum interaction gate,besides electric and magnetic field controls, there are additional twoways in which an electron can be controlled: classically and by anotherquantum state. Classical control uses, for example, a control voltagethat is generated by a classic electronic circuit. A voltage is imposedthat impacts the behavior of the electrons. Besides classic control, anelectron can also be controlled by another electron. If that electron isin a quantum state, then the electron can be controlled using anotherquantum state. In addition, both classic and quantum control can be usedat the same time.

A diagram illustrating a target semiconductor quantum gate with classicelectronic control is shown in FIG. 10A. In one embodiment, classicelectronic control 352 alone is used to control the target semiconductorquantum interaction gate 350.

A diagram illustrating a target semiconductor quantum gate with quantumcontrol is shown in FIG. 10B. In another embodiment, quantum control 362alone is used to control the target semiconductor quantum interactiongate 360.

A diagram illustrating a target semiconductor quantum gate with bothclassic electronic control and quantum control is shown in FIG. 10C. Inanother embodiment, both classic electronic control 372 as well asquantum control 374 are used to control the target semiconductor quantuminteraction gate 370. In this case, the target semiconductor quantumgate comprises, for example, both a control gate for controlling thetunneling barrier but also uses quantum control whereby one or moreadditional electrons provide control. As described supra, the controlvoltage applied to the control gate impacts the Rabi oscillationfrequency. In addition, bringing an electron into proximity of thetarget electron, also impacts the Rabi oscillation frequency.

Note that the way in which the quantum control NOT control gate as wellof other common types of control gates, e.g., ancillary, Pauli, SWAP,etc. are realized, electrons are brought into close proximity along withuse of classic electronic control circuits providing the control signalon the gate. It is also possible to control these gates with a quantumstate of an electron.

A diagram illustrating an example qubit with classic electronic controlis shown in FIG. 11A. The qubit comprises two qdots 382 in a ‘dog bone’configuration, particle 386, control gate 384 coupled to a classicelectronic control circuit 380. As discussed supra, in one embodiment, aclassic electronic circuit controls the voltage on the control gate of aqubit which changes its Rabi or occupancy oscillation thus impacting howfast the electron tunnels back and forth. Note that Rabi oscillation isthe interference between two very high frequency eigenfunctions.

A diagram illustrating an example qubit with both classic electroniccontrol and quantum control is shown in FIG. 11B. The target qubitcomprises two qdots 392, particle 396, control gate 394 coupled to aclassic electronic control circuit 390. In addition, a second qubit(control) having two qdots 391, particle 395, and control gate 393 is inrelatively close proximity to the target qubit. The particle in thetarget qubit tunnels back and forth at the Rabi oscillation under theclassic electronic control. Now, however, a control electron 395 isbrought into proximity. If the electron is sufficiently far away, thenthe Rabi oscillation is faster. If the control electron is broughtrelatively close like it is in the case shown in FIG. 11C, the Rabioscillation becomes slower (frequency F₁). Thus, the Rabi oscillation ofthe target qubit can be controlled by the proximity of another electron.

In one embodiment, classic electronic control means controlling theamplitude and pulse width of the control signal applied to the controlgate. In another embodiment, this can be achieved without using anydirect electronic control. The proximity of the neighboring controlelectron to the target qubit is used to control it. Note that thisassumes the potential on the control gate of the target qubit is notfloating but such that the tunneling barrier is lowered and the electronis free to move between the qdots. If the control gate voltage isstable, the electronic control does not impact the operation and justthe quantum control dominates, i.e. the other electron impacts theoperation of the target qubit. Thus, any combination of electroniccontrol only, quantum control only, or both of them can be used.

A diagram illustrating an example qubit having quantum control with thecontrol carrier at a close distance is shown in FIG. 11C. The targetqubit comprises two qdots 400, particle 404, control gate 402 coupled toa classic electronic control circuit (not shown). In addition, a secondqubit having two qdots 406, particle 409, and control gate 408 is inrelatively close proximity to the target qubit. In this case, thecontrol carrier is near the target qubit and provides control thereof.

A diagram illustrating an example qubit having quantum control with thecontrol carrier at a far distance is shown in FIG. 11D. The target qubitcomprises two qdots 410, particle 414, control gate 412 coupled to aclassic electronic control circuit (not shown). In addition, a secondqubit having two qdots 416, particle 419, and control gate 418 is inrelatively far from the target qubit. In this case, the control carrieris far from the target qubit and has less impact thereon. In this case,the resultant Rabi oscillation is faster (frequency F₂).

As described supra, a quantum state can be described by the two angles θand φ. The angle θ determines the split between the two base stateswhere θ represents the actual state of the electron, i.e. where it'sprobabilities are versus the two qdots of a qubit for example. The angleφ represents the procession movement in the Bloch sphere. A diagramillustrating an example position based quantum system with θ angle and φangle electric field control is shown in FIG. 12A. In this embodiment, amore precise description of the system is provided, where in a positionbased quantum interaction system 420 an electric field is used tocontrol the angle θ (block 422) and an electric field is used to controlthe angle φ (block 424). Note that it is preferable to use electricfields for control because electric fields are generated by voltages andsignals are transported on wires which can be easily produced byintegrated circuits.

Inductors that create magnetic fields can also be fabricated inintegrated circuits. A diagram illustrating an example position basedquantum system with θ angle electric field control and φ angle magneticfield control is shown in FIG. 12B. In this embodiment, an electricfield is used to control the angle θ, i.e. the position of the electron(block 432) and an auxiliary magnetic field is used to control the angleφ of the quantum state (block 434) of a position based quantuminteraction system 430.

A diagram illustrating an example position based quantum system with θangle magnetic field control and φ angle electric field control is shownin FIG. 12C. The flip case is also possible where a magnetic field isused to control the angle θ, i.e. the position of the electron (block442) and an electric field is used to control the angle φ of the quantumstate (block 444) of a position based quantum interaction system 440.

A diagram illustrating an example position based quantum system with θangle electric field control and no φ angle external control is shown inFIG. 12D. In this embodiment, an electric field is used to control theangle θ (block 452) and no external control is used to control the angleφ of a position based quantum interaction system 450. It is implied thatangle φ will be whatever the quantum system yields at a given point.Note that the angle φ is not random but multiple qubits interacting mayresult in phases that are not synchronized. Thus, the difference φ1minus φ2 between the electrons changes over time and this will impactthe solution or the outcome of the quantum operation.

Most of the structures described supra use charge qubits and qdots thatare electrically controlled via an electric field. A more generalquantum structure can use hybrid electric and magnetic control. Themagnetic field can be generated with an inductor or a resonator. Adiagram illustrating an example quantum interaction gate with electricfield main control and magnetic field auxiliary control is shown in FIG.12E. The structure comprises a quantum interaction gate 830 locatedwithin an auxiliary magnetic control 832. The main control is electric.In this example, the hybrid electric and magnetic control is applied toa double-V structure using tunneling through local depleted regions. Oneor more gates can be under the control of a magnetic field generationstructure. The control is local since only one interaction structuresees the strong magnetic field from the inductor (or resonator). Notethat the size and shape of the magnetic field generator can vary. Notethat the control for the electric and magnetic field generator isprovided by the external support unit 834 and clock generator circuit836 which includes a low frequency (LF) reference generator circuit 838and power amplifier (PA) 839.

A diagram illustrating an example quantum interaction gate with electricfield main control and local and global magnetic field auxiliary controlis shown in FIG. 12F. The structure comprises a quantum interaction gate842 located within a magnetic control 844, and electric control 840. Inthis example, the hybrid electric and magnetic control is applied to adouble-V structure using tunneling through local depleted regions withpartial fin-to-gate overlap. One or more gates can be under the controlof a magnetic field generation structure. The control is local sinceonly one interaction structure is seeing the strong magnetic field fromthe inductor (or resonator). Note that the size and shape of themagnetic field generator can vary. Note that for clarity sake theexternal support unit and clock generation circuit are not shown butincluded in the circuit as in FIG. 12E.

A diagram illustrating an example quantum interaction gate with localmagnetic field control is shown in FIG. 12G. The structure comprises aquantum interaction gate with two local magnetic controls 850, 852covering different portions of the interaction gate. In this example,both local magnetic controls are applied to a multiple-V structure usingtunneling through local depleted regions. One or more gates can be underthe control of a magnetic field generation structure. The control islocal since only one interaction structure is seeing the strong magneticfield from the inductor (or resonator). Note that the size and shape ofthe magnetic field generator can vary. Note that for clarity sake theexternal support unit and clock generation circuit are not shown butincluded in the circuit as in FIG. 12E.

In the case of a larger quantum core, multiple inductors can be used tocreate local magnetic control fields. Alternatively, a global magneticcontrol can be used, which impacts two or more quantum structures at atime. A diagram illustrating an example grid array of programmablesemiconductor qubits with both global and local magnetic fields is shownin FIG. 12H. The structure comprises a plurality of qubits 866 arrangedin rows and columns, a plurality of local magnetic field controls 864(per quantum gate or a small group of quantum gates), a global magneticfield control 862, and an electric control 860. With global magneticcontrol, multiple quantum structures are controlled by the same magneticfield. One example use for the magnetic field is to select the spinorientation of the particles that are loaded in the quantumstructures/core.

A diagram illustrating an example quantum processing unit incorporatinga plurality of individual control signal DACs is shown in FIG. 13A. Thequantum processing unit, generally referenced 810, comprises a digitalcontrol circuit 814, a plurality of individual DACs 816 whose analogcontrol signal outputs are input to n control gates in quantum core 818.In operation, the quantum processing unit communicates with the externalworld via the external support unit 812. The external support unit maycomprise a PC, a computer, an FPGA board, or any other kind of externalelectronic system or computing device. The external support unitinteracts with the digital control 814. The quantum core 818 comprises aplurality of quantum circuits with quantum interaction gates and quantumwells with associated control terminals. A control signal for eachcontrol terminal is provided. This includes, for example, the controlgates of the imposers, gates in the sources and the drains of theinterface devices, etc. These circuits all need to have dedicatedcontrol signals which are generated in this embodiment by individualDACs 816.

A diagram illustrating an example quantum processing unit incorporatingshared control signal DACs is shown in FIG. 13B. The quantum processingunit, generally referenced 820, comprises a digital control circuit 824,a plurality of shared DACs 826 whose analog control signal outputs areinput via a multiplexer 827 to n control gates in quantum core 828. Inthis embodiment, the DACs are shared among the control gates in thequantum core. The digital control (e.g., DSP) functions to compute thecontrols needed which are converted to analog via an analog controllerincluding the shared DACs. The result is a plurality of analog signalsthat go to the different control lines of the quantum core. Due to therelatively high number of control lines needed, the control circuit isshared between two or more ports thereby reducing the number of controlsignals.

In one example embodiment, 32 control circuits are required to controlthe different aspects of a single qubit. For two qubits, the number ofcontrol circuits doubles to 64. In the case of a thousand qubits, thenumber balloons to 32,000 control circuits. With higher numbers ofqubits the control circuitry grows very quickly. Thus, sharing controlcircuits between different nodes using the same hardware isadvantageous. Note that any control signals that must be controlledsimultaneously cannot be shared. There is, however, some spatialdistribution of quantum interaction gates whereby not all controlsignals need to be controlled at the same time.

A diagram illustrating an example quantum processing unit incorporatinga combined amplitude and timing circuit is shown in FIG. 14A. Thequantum processing unit, generally referenced 460, comprises interface(I/F) and digital control unit (DSP) 464, quantum control block 466including combined amplitude and timing (pulse width) circuit 468, andquantum interaction gate, circuit, or core 469. The quantum processingunit 460 interfaces with the outside world via the external support unit462. The digital control unit functions to calculate the differentcontrol signals needed to create a given quantum operation. In oneembodiment, the digital control unit is programmable. The interfacereceives commands that determine what kind of control signals andcircuits are to be generated. Once determined, the digital control unitinstructs the combined amplitude and timing control circuit 468 togenerate the analog control signals required to perform the particularquantum operation in the quantum interaction gate, circuit, or core. Theprecise amplitude and timing (i.e. pulse width) is calculated for eachcontrol signal. Note that in this embodiment, the amplitude as well asthe timing for the control signals are generated together via circuit468.

Alternatively, the amplitude and timing can be generated separately. Adiagram illustrating an example quantum processing unit incorporatingseparate amplitude and timing circuits is shown in FIG. 14B. The quantumprocessing unit, generally referenced 470, comprises interface (I/F) anddigital control unit (DSP) 474, quantum control block 476 includingseparate amplitude control circuit 478 and timing control (i.e. pulsewidth) circuit 479, and quantum interaction gate, circuit, or core 477.The quantum processing unit 470 interfaces with the outside world viathe external support unit 472. The digital control unit functions tocalculate the different control signals needed to create a given quantumoperation. In one embodiment, the digital control unit is programmable.The interface receives commands that determine what kind of controlsignals and circuits are to be generated. Once determined, the digitalcontrol unit instructs the separate amplitude control 478 and timingcontrol 479 circuits to generate the analog control signals required toperform the particular quantum operation in the quantum interactiongate, circuit, or core. The precise amplitude and timing (i.e. pulsewidth) is calculated for each control signal.

A description of the various types of control signals that can beapplied to the control terminals will now be presented. A diagramillustrating a first example control gate signal is shown in FIG. 15A.The control signal 500 has a low value and a high value and transitionsvery quickly from low to high and high to low. Such control signals areuseful for quantum switching operations and quantum switching machines.A diagram illustrating a second example control gate signal is shown inFIG. 15B. The control signal 502 has low and high values but a slow risetime and a quick fall time. A diagram illustrating a third examplecontrol gate signal is shown in FIG. 15C. The control signal 504 has lowand high values but a quick rise time and a slow fall time. A diagramillustrating a fourth example control gate signal is shown in FIG. 15D.The control signal 506 has low and high values and slow rise and falltimes. Control signals with slow rise and/or fall times are useful inrealized annealing quantum interaction gates and quantum machines.

A mixture of control signals 500 and 506 can be used in quantum machinesthat do both annealing and switching operations, but not at the sametime for a given qubit. Some qubits may be switching and some annealing.In addition a single qubit may have a hybrid operation using the controlsignals 502, 504. A slow rising edge means an adiabatic state change asRabi oscillation tunneling is achieved. Stopping the Rabi oscillation,stops the tunneling sharply. So one edge is fast when one edge is slow.The opposite case is also possible, i.e. the rising edge is fast and thefalling edge is slow. Enabling the Rabi oscillation quickly obviatesadiabatic but switching it off enables adiabatic. Thus, control signals500, 502, 504, 506 are four main control signals suitable for a switchedquantum computer (500), annealing quantum computer (506), and hybridswitched annealing quantum computers (502, 504).

A diagram illustrating a fifth example control gate signal is shown inFIG. 15E. The control signal 508 comprises a pulse with quick rising andfalling edges and a step 509 in the ‘on’ portion. As described supra,quantum tunneling is exponentially dependent on the tunneling barrier.If amplitude in the on state is changed even slightly this can impactthe frequency of the Rabi oscillation quite significantly and thereforethe frequency of the tunneling which can change the outcome of thequantum operation. The slight step 509 in the amplitude thus slightlyimpacts the frequency of the Rabi oscillation.

A diagram illustrating a sixth example control gate signal is shown inFIG. 15F. The control signal 510 in this case comprises a step 511 inthe ‘off’ state. In this case, the on state is constant in amplitude butthe off state changes. This is performed, for example, because thequantum system is very sensitive in the on state and very insensitivewhen in the off state. Thus, much higher amplitude changes in the offstate are required to make any kind of change in the state of thesystem. A diagram illustrating a seventh example control gate signal isshown in FIG. 15G. The control signal may include changes in amplitudeboth for the on and off states. The control signal 512 in this case is acombination of the two control signals 508, 510 with a step 513 in theon state as well as a step 515 in the off state.

A diagram illustrating an eighth example control gate signal is shown inFIG. 15H. The control signal 514 comprises two pulses where the pulsewidths are different. Thus, the control signal may comprise two or morepulses but they do not necessarily have to be the same width. Multiplepulses of different widths may be used.

A diagram illustrating a ninth example control gate signal is shown inFIG. 15I. The control signal 516 comprises two pulses in this case. Theamplitude and pulse width set in accordance with the desired quantumoperation. A diagram illustrating a tenth example control gate signal isshown in FIG. 15J. The control signal 518 in this case comprises aplurality of pulses.

A diagram illustrating an eleventh example control gate signal is shownin FIG. 15K. The control signal 520 comprises a train of pulses wherethe amplitude of each may be different. The dotted line 522 highlightsthe different amplitudes of the pulses.

A diagram illustrating a twelfth example control gate signal is shown inFIG. 15L. The control signal 524 comprises a train of pulses where theamplitude and pulse width of each may be different. The dotted line 526highlights the different amplitudes of the pulses. This pulse train canbe viewed as the most generalized pulse control signal.

A diagram illustrating a thirteenth example control gate signal is shownin FIG. 15M. The control signal 528 comprises a pulse having fast risingand falling edges and a sine wave 530 in the on portion of the pulse. Inthis case, the sine wave is in the on portion of the pulse but is notlimited to this. In one embodiment, the sine wave is used to control theangle φ of a quantum interaction gate and a quantum structure. The baseenergy of a quantum state can be changed by having an oscillatoryexcitation for the control signal. Thus, using a sine wave an average ofzero can be obtained or any desired average depending on how many cyclesare selected.

A diagram illustrating a fourteenth example control gate signal is shownin FIG. 15N. The control signal 532 comprises a pulse having fast risingand falling edges and a sine wave 534 in a portion of the on state ofthe pulse. Note that the angle φ can be manipulated by using anoscillatory signal either on the entire state (control signal 528) or apart thereof (control signal 532).

A diagram illustrating a fifteenth example control gate signal is shownin FIG. 15O. The control signal 536 comprises a pulse with fast rise andfall times for the on state. An oscillatory signal 538, e.g., sine wave,is inserted in the off state.

A diagram illustrating a sixteenth example control gate signal is shownin FIG. 15P. The control signal 540 comprises two pulses each with fastrise and fall for the on states and an oscillatory signal 542 in the offstate between them.

A diagram illustrating a seventeenth example control gate signal isshown in FIG. 15Q. The control signal 544 comprises two pulses where onehas an oscillatory signal 546 in the on state of one of the pulses andan oscillatory signal 548 in the off state as well.

A diagram illustrating an eighteenth example control gate signal isshown in FIG. 15R. The control signal 550 comprises a plurality ofpulses of different amplitudes and pulse widths where one or more pulseshas an oscillatory signal 554 in the on state.

Note that the frequency of the oscillatory signals may vary from signalto signal and pulse to pulse. In addition, the control pulses may havedifferent amplitudes and different widths. Further, any combinations ofthe above control signal features may be generated.

In the case where a quantum interaction gate comprises two qubits,typically two control signals are required, rather than one. The controlsignals are typically what determines the functionality of the quantumcircuit. A diagram illustrating a first example pair of control gatesignals G_(A) and G_(B) is shown in FIG. 16A. Control signal G_(A) 560comprises a pulse with fast rising and falling edges and control signalG_(B) 562 remains static in the off state at least for the time that isobserved. These control signals provide a control NOT functionality tothe two qubits.

A diagram illustrating a second example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16B. Control signal G_(A) 564 comprisesa pulse with fast rising and falling edges and control signal G_(B) 566comprises a pulse with fast rising and falling edges but skewed in timefrom G_(A). Each gate of the qubits is pulsed one at a time.

A diagram illustrating a third example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16C. Control signal G_(A) 568 comprisesa pulse with fast rising and falling edges and control signal G_(B) 570also comprises a pulse with fast rising and falling edges simultaneouswith G_(A). These control signals provide a quantum SWAP gate. Note thatif both qubits are pulsed at the same time but with slow edges thequantum annealing structure can be realized.

A diagram illustrating a fourth example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16D. Control signal G_(A) 572 comprisesa pulse with fast rising and falling edges and a first amplitude andcontrol signal G_(B) 574 comprises a pulse with fast rising and fallingedges and a second different amplitude and simultaneous with G_(A). Thearrows in the x-direction indicate that the low state is the same forthe two control signals. The amplitudes, however, are different. Thismeans that the tunneling speed of the G_(A) qubit will be different fromthe tunneling speed of G_(B) qubit.

A diagram illustrating a fifth example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16E. Control signal G_(A) 576 comprisesa pulse with fast rising and falling edges and a first off stateamplitude and control signal G_(B) 578 comprises a pulse with fastrising and falling edges and a second different off state amplitude,simultaneous with G_(A). In this case, the arrows in the x-dimensionindicate that the on state amplitude of the two control signals are thesame. The amplitude of the off state, however, is different. Thus, G_(A)and G_(B) fall differently, G_(A) goes lower while G_(B) goes lesslower. This is called asymmetric control where the control signals arenot the same.

A diagram illustrating a sixth example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16F. Control signal G_(A) 580 comprisesa pulse with fast rising and falling edges and control signal G_(B) 582comprises a pulse with fast rising and falling edges with differenttiming than G_(A). The two control signals partially overlap in time.This causes an initial phase shift when G_(A) goes high. As G_(B)quickly switches on it overlaps with G_(A) resulting in a quantum SWAPoperation. G_(A) then finishes and G_(B) continues resulting in anotherphase shift.

A diagram illustrating a seventh example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16G. Control signal G_(A) 584 comprisesa pulse with fast rising and falling edges and control signal G_(B) 586comprises a pulse with fast rising and falling edges, simultaneous withG_(A). Note that large amplitude control signals are needed to achieveproper tunneling between quantum states. In this example, however,rather than achieve full tunneling, only a slight change of the angle ofthe state is achieved by applying a lower amplitude for both G_(A) andG_(B). This can be used, for example, in quantum error correction.Consider a quantum state where the electrons are interacting with eachother. All the information is in the entangled quantum state, but errorsoccurred due to noise in the system, etc. Raising the gate voltages ofthe different gates by a small amount allows the state to readjustitself to compensate for the errors that were created but it does notchange it fundamentally.

A diagram illustrating an eighth example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16H. Control signal G_(A) 588 comprisesa pulse with fast rising and falling edges and control signal G_(B) 590comprises a pulse skewed in time from G_(A) with fast rising and fallingedges and an oscillatory signal in the on state. In this example, thecontrol signals provide a control NOT operation followed by anoscillatory signal on G_(B) where the angle φ of rotation of one of thequbits or both of them is corrected.

A diagram illustrating a ninth example pair of control gate signalsG_(A) and G_(B) is shown in FIG. 16I. Control signal G_(A) 592 comprisesa pulse with fast rising and falling edges with an oscillatory signal inthe off state and control signal G_(B) 594 comprises a pulse skewed intime from G_(A) with fast rising and falling edges. In this example, thecontrol signals provide a control NOT operation followed by anoscillatory signal on G_(B) where the angle φ of rotation of one of thequbits or both of them is corrected.

A diagram illustrating an example quantum processing unit with separateamplitude and time position control units is shown in FIG. 17A. Thequantum processing unit 600 comprises digital signal processing control(DSP) circuit 604, amplitude DAC control unit 614, pulse width and timeposition DAC control unit 618, injector amplitude DACs 632, imposeramplitude DACs 634, detector amplitude DACs 636, injector time and pulsewidth DACs 638, imposer time and pulse width DACs 640, detector time andpulse width DACs 642, and quantum core 644. The quantum core 644comprises a quantum circuit 650, imposers 646, injectors 648, anddetectors 652.

The quantum computing core 644 has a certain structure depending on thedesired application along with injector, imposer, detector, and reset(not shown) circuits. The required control signals to these circuits aregenerated by the DACs electronic circuits in this example. It isappreciated that they can be generated not only with digital to analogcontrol circuits but by using pure analog circuitry as well. Regardlessof the mechanism, ultimately, analog control is required. The pulseshaping can be performed by an analog circuit, digital circuit, or acombination thereof.

Thus, a plurality of DACs provide the control signals that are input tothe quantum structure. In one embodiment, 32 control signals, i.e. 32DACs, are required for each qubit. Although the amplitude and timing canbe controlled together, it is typically easier to control themseparately as shown in FIG. 17A. Therefore, some DACs are dedicated tocontrolling amplitude and others are dedicated to controlling timing ofthe signals.

The quantum processing unit interfaces to the outside world via thedigital control (DSP) 604 and the external support unit 602. Inaddition, each of the amplitude DAC control unit and the pulse width andtime position DAC control unit comprise calibration circuits 616, 620,respectively. In one embodiment, calibration circuits (also referred toas calibration loops) are used to compensate for variations in thecircuits and to enable generation of precise amplitude and timing.Without the calibration loops, the amplitude and timing of the controlsignals may be inaccurate due to process variability, temperaturevariability, and other environmental variabilities resulting ininaccuracies in the quantum structure.

In addition, the quantum processing unit receives a high frequency clock624 that is provided externally. The clock is input to a clock buffer626 followed by a multiphase clock divider 628. Using an edge selector622, the multi-phase signal is used to create pulses that have variouspulse widths and positions in time. A memory based pulse generator 630functions to select a sequence to use for each of the control pulses.

Moreover, the quantum processing unit comprises several sensors,including a local temperature sensor 608, process sensor 610 to detectprocess corners for the chip, and magnetic field sensor 612 to detectthe magnetic field of the earth or other perturbing electromagneticfields in proximity, all connected to the digital control 604. Forexample, if a perturbation on the system is detected, a temperatureprocess adjustment or an environmental adjustment that changes thedigital control can be performed. This, in turn, will change theamplitude and the timing that goes into the DACs thereby changing thesignals input to the quantum structure to compensate for those externalfactors.

A diagram illustrating an example quantum processing unit with separateamplitude and time position control units and control adjustments forqubit entanglement is shown in FIG. 17B. The quantum processing unit,generally referenced 670, comprises digital control (DSP) circuit 674,amplitude and time/pulse width (PW) DAC control unit for qubit A 676,amplitude and time/pulse width (PW) DAC control unit for qubit B 680,control adjustment circuit 678 for qubit A to qubit B entanglement,amplitude DACs 682 for qubit A, time and pulse width DACs 684 for qubitA, amplitude DACs 686 for qubit B, time and pulse width DACs 688 forqubit B, and quantum core 706. The quantum core 706 in this examplecomprises two qubits, namely qubit A 694 and qubit B 700. Associatedwith qubit A are injector circuits 692, imposer circuits 690, anddetector circuits 696. Associated with qubit B are injector circuits698, imposer circuits 704, and detector circuits 702. In addition, thedigital control circuit 674 communicates with the external support unit672. Note that for clarity sake, individual DACs for the injector,imposer, and detector circuits for both qubits as well as othercircuitry are not shown in FIG. 17B. It is understood, however, that thequantum processor unit 670 is constructed similarly to the quantumprocessor unit 600 of FIG. 17A.

Note that the voltage of the control signals and timing levels for asingle qubit are relatively known and have a certain value. Given twoqubits, however, that are entangled, the voltage level needed to obtaina Rabi oscillation with multiple entangled electrons is slightlydifferent from that for a separate electron. This is because theseparate electron behaves differently but in a predictable way fromentangled electrons. In addition, calibration of the system is generallystraightforward for a single electron. With entangled electronsperforming control adjustment is based on the number of qubits that areentangled. The control circuit 678 functions to change slightly theamplitude and the timing of the control signals to compensate for thefact that the two qubits are in entangled states.

As described supra, the quantum state can be represented by two phases θand φ. The θ angle gives the split of the electron's wavefunctionbetween two or more qubits. The φ angle cannot be measured externallybut can be impacted externally and thus be changed. Although φ cannot bemeasured in a single qubit it can be measured in a two-qubit interactionresulting from the impact of the difference between the two φ angles.

A diagram illustrating a first example qubit with φ angle control isshown in FIG. 18A. The quantum interaction gate, generally referenced710, is shown for illustration purposes only. It is appreciated thatnumerous other quantum structures may be used as well. The interactiongate comprises a continuous well 720, plurality of control gates 722,local depletion regions 732 for tunneling, interface devices/wells 730,728, particle 724 which can be in the full or split state, reset circuit714, injector circuit 716, imposer circuit 718, detector circuit 712,and φ angle control circuit 726.

The angle φ of the quantum state can be changed by applying anadditional static voltage or potential V_(φ). The φ angle controlcircuit 726 provides a potential that is applied at one end of thequantum structure. Via the control gates this potential is propagated inclose proximity to the particle. Note that the potential should come inclose proximity to be effective. Once the φ angle control potential isin close proximity to the electron it will impact the phase. Forexample, if a particle is split between two qdots, and a static controlpotential is brought in close proximity to a quantum state or anelectron, this will impact the phase φ thereof.

A diagram illustrating a second example qubit with φ angle control isshown in FIG. 18B. The quantum interaction gate, generally referenced740, comprises a continuous well 754, plurality of control gates 750,local depletion regions 756 for tunneling, interface wells/devices 752,758, 751, particle 753 which can be in the full or split state, resetcircuit 742, injector circuit 744, imposer circuit 746, detector circuit748, and φ angle control circuit 755.

In this alternative embodiment, the injector and reset circuits are onone end and the detector circuit the other. The electron is injectedinto the quantum well on the left side and exits on the right. In thiscase, the top interaction qdot has another quantum dot linked to it. A φangle control circuit 755 generates a static potential V_(φ), that isapplied to interface device 751 to control the potential on the twoqdots adjacent to the quantum structure which functions to change theangle φ of the quantum state.

Note that the φ angle control voltage is not applied to a gate sincethat would affect the tunneling and impact the angle θ. It is desiredthat the electron stays in exactly the split state it is in. Only theprocession is to be affected and the procession is impacted by a staticelectric field. The static electric field is applied from something thatis in close proximity. The well is the closest place to apply thevoltage and this is done via an interface device coupled to a classiccircuit. It is appreciated that the static control voltage can beapplied via metal, poly or a well.

In another embodiment, the electrostatic field created by the φ anglecontrol voltage can be applied via one or more back gates rather thanvia front gates. A diagram illustrating a third example qubit with φangle control is shown in FIG. 18C. The example quantum interactiongate, generally referenced 760, comprises a continuous well layer 768,BOX oxide 766 and an additional layer 772 under the oxide 766 referredto as a back gate. In this embodiment, the interaction gate comprisesboth front gate control 762 and back gate control 764. The φ anglecontrol voltage is applied to the back gate control from the top sidewhere it is electrically connected to back layer 772 via metal 774 andvia well 770.

Note that the back gate under the quantum well 768 is reached via metal774 and a portion of well 770 that penetrates through the oxide to awell 772 under the oxide 766. Thus by controlling the voltage at theback gate control terminal 764 the potential of the back gate well canbe controlled which changes the angle φ in the structure.

A diagram illustrating an example pair of qubits with φ angle control isshown in FIG. 18D. The example quantum interaction gate, generallyreferenced 780, comprises two qubits. The left qubit comprises acontinuous well layer 792, BOX oxide 790 and an additional layer backgate 798 under the oxide 790, front gate control #1 782, back gatecontrol #1 786, metal 804, and well 796. The φ angle control voltage isapplied to the back gate control from the top side where it iselectrically connected to back layer 798 via metal 804 and well 796. Theright qubit comprises a continuous well layer 794, BOX oxide 790 and anadditional layer back gate 802 under the oxide, front gate control #2784, back gate control #2 788, metal 808, and well 800. The φ anglecontrol voltage is applied to the back gate control from the top sidewhere it is electrically connected to back layer 802 via metal 808 andwell 800.

Thus, in this embodiment, multiple quantum sections have separatebackside connections. In this manner, the angle φ can be impacteddifferently in the left qubit versus the right qubit. Note that what isimportant is the difference between φ1 and φ2 of the two qubits and nottheir absolute value. Therefore, if there is a difference in the anglesthat impacts the quantum results in a negative way, the φ angle can becontrolled via the back gate such that the two angles are aligned to apoint where φ1 minus φ2 does not pose a problem for the quantumoperation.

A diagram illustrating an example planar and 3D quantum well structurefabricated using bulk semiconductor processes is shown in FIG. 19A. Thequantum structure comprises a low doped substrate 1100 with sparsedopants 1104 far from each other on which a planar well 1106 isfabricated containing a quantum electron 1103 (i.e. an electron whosequantum features are distinct and can be exploited). Parasiticinteractions 1105 typically occur between the dopants 1104 and quantumparticle (e.g., electron, hole, etc.) 1103. In addition, a 3D well 1108with quantum electron 1103 can be fabricated on the substrate. Note thata well is a semiconductor layer realized in a semiconductor physicalstructure as a result of the designated processing flow. The well can beundoped, i.e. intrinsic, or it can be doped. The lower the concentrationof dopants in a well, the better suited it is for quantum applicationssince less dopants and free carriers are available to interact with thequantum particles which result in decohering quantum information. If thewell sits directly on a semiconductor substrate, the process is referredas a bulk semiconductor process.

A diagram illustrating an example planar and 3D quantum well structurefabricated using silicon on insulator (SOI) semiconductor processes isshown in FIG. 19B. The quantum structure comprises a low doped substrate1110 with sparse dopants 1119 far from each other, an oxide layer 1112on which a planar well 1114 is fabricated containing a quantum electron1118. Parasitic interactions 1111 typically occur between the dopants1119 and quantum particle 1118. In addition, a 3D well 1116 with quantumelectron 1118 can be fabricated on the oxide.

If the well is separated from the semiconductor substrate by an oxidelayer, the technology process is referred to as silicon on insulator(SOI). Note that planar processes provide layers that extend mostlyparallel with the substrate surface, while 3D processes provide layersthat extend on a direction perpendicular to the substrate surface.

In general, there are two ways in which a well can be controlled. Oneway is to drive or impose the well with a voltage potential. A diagramillustrating an example planar and 3D quantum well structure fabricatedusing bulk semiconductor processes and potential driven electrically isshown in FIG. 19C. The quantum structure comprises a substrate 1120 withdense and close dopants 1126 on which a planar well 1124 is fabricatedcoupled to a drive voltage V_(drive) 1128. In addition, a 3D well 1122coupled to drive voltage V_(drive) 1129 can be fabricated on thesubstrate. The potential on the wells is determined by sources thatdrive them directly V_(drive). Although the potential varies with time,it does not vary freely based on the position of a given electron orhole. The substrate of classic electronic circuits can have a largenumber of dopants or a moderate or lower number of dopants.

Another way to control a well is to have another quantum well having anelectron in close proximity to the first well. A diagram illustrating anexample planar and 3D quantum well structure fabricated using silicon oninsulator (SOI) semiconductor processes and floating potential dependenton quantum particles is shown in FIG. 19D. The quantum structurecomprises a low doped substrate 1130 with sparse dopants 1138 far fromeach other, an oxide layer 1132 on which a planar well 1134 isfabricated containing a quantum electron 1136. Parasitic interactions1131 typically occur between the dopants 1138 and quantum particle 1136.In addition, a 3D well 1139 that can contain quantum electron 1136 canbe fabricated on the oxide.

In this embodiment, the quantum wells are floating and their potentialcan change due to the presence of one or few quantum particles. Notethat it is preferable to realize quantum semiconductor structures in SOIprocesses, since the oxide layer minimizes the de-coherence from thesubstrate. A high resistivity substrate, i.e. low doped substrate, helpsfurther reduce the substrate de-coherence. In one embodiment, thesemiconductor substrate is eliminated altogether and replaced with aninsulating material. This eliminates the substrate de-coherence due todopants.

A diagram illustrating example imposing on the potential of a floatingplanar quantum well using an electrically, i.e. voltage, driven adjacentlayer is shown in FIG. 19E. The quantum structure comprises a low dopedsubstrate 1140 with sparse dopants 1147 far from each other, an oxidelayer 1142 on which a planar well 1148 is fabricated containing aquantum electron 1145. Parasitic interactions 1141 typically occurbetween the dopants 1147 and quantum particle 1145. In this embodiment,the potential of the quantum well has an imposing, i.e. control, appliedfrom an adjacent side 1143 or top layer 1149 that has its potentialdriven with an electric source equivalent circuit 1146. Either way, thevoltage can be imposed from a piece of metal, gate material, fromanother well, from a piece of poly, etc. Note that although SOIprocesses are shown, bulk processes can be used as well.

A diagram illustrating example imposing on the potential of a floatingplanar quantum well using a floating layers with quantum particles isshown in FIG. 19F. The quantum structure comprises a low doped substrate1153 with sparse dopants 1159 far from each other, an oxide layer 1154on which a planar well 1155 is fabricated containing a quantum electron1158. Parasitic interactions 1151 typically occur between the dopants1159 and quantum particle 1158.

In this case, top imposing is achieved using another quantum particle1152 in a top layer 1156. Alternatively, side imposing is achieved usinganother quantum particle 1152 with a certain quantum state in a sidelayer 1157. Note that the goal is to change the field around theparticle that is to be controlled. The other particles, e.g., 1152,function to create an electric field that influences the particle 1158.Imposing on a quantum particle from another particle results inentanglement which is the basis of the quantum computation.

A diagram illustrating example imposing on the potential of a floating3D quantum well using an electrically driven adjacent layer is shown inFIG. 19G. The quantum structure comprises a low doped substrate 1160with sparse dopants 1169 far from each other, an oxide layer 1162 onwhich a 3D fin 1166 is fabricated containing a quantum electron 1168.Parasitic interactions 1161 typically occur between the dopants 1169 andquantum particle 1168. Note that although SOI implementations are shown,bulk processes may be used as well.

The potential of the 3D quantum fin 1166 has an imposing, i.e. control,from an adjacent side 1167 or top layer 1165 that in turn has itspotential driven with an electric source 1163 equivalent circuit. Theimposing layers may comprise gate material, metal, poly, other wells,etc.

A diagram illustrating example imposing on the potential of a floating3D quantum well using floating layers with quantum particles is shown inFIG. 19H. The quantum structure comprises a low doped substrate 1170with sparse dopants 1179 far from each other, an oxide layer 1172 onwhich a 3D fin 1176 is fabricated containing a quantum electron 1173.Parasitic interactions 1171 typically occur between the dopants 1179 andquantum particle 1173. Note that although SOI implementations are shown,bulk processes may be used as well.

In this embodiment, the imposing on the potential of the 3D quantum well1176, i.e. fin, is realized by another quantum particle, i.e. quantumstate. The imposing quantum particle 1174 is located on an adjacent side1177 or top layer 1175. Imposing on a quantum particle 1173 from anotherparticle 1174 results in entanglement, which is the basis of the quantumcomputation.

The operation of the controlled quantum shift register will now bedescribed in more detail. A diagram illustrating initialization of anexample controlled semiconductor shift register (or quantum structurehaving bifurcation for transporting particles) is shown in FIG. 20A. Theexample quantum shift register, generally referenced 1180, comprises aplurality of planar qdots 1182 with tunneling path through oxide 1188and arranged in sequential (daisy-chain) fashion one next to the other,control gate (or terminal) 1184, and particle 1181. Imposing voltagepulses V_(IA), V_(IB), V_(IC), and V_(ID), are applied to control gates1184, 1185, 1186, and 1187, respectively. Note that any semiconductorprocess may be used to construct the quantum shift register. Note thatthe shift register is operative to transport both full quantum particlesas well as split quantum particles (i.e. quantum state).

At time 1189, the shift register is in an initial state whereby aparticle is situated in the left most qdot. Note that other positionsmay be assumed for the initial condition. A full particle or asplit/entangled quantum state can be used as initial state. The controlgates maintain the tunneling barriers high thereby keeping the particle1181 in the left most qdot.

Note that in this example, lowering the imposing voltage lowers thetunneling barrier. Depending on the implementation, however, it may bethe opposite where raising the imposing voltage lowers tunnelingbarrier. In addition, as described supra, if a pulse having a pulsewidth of 27 c is applied, the particle will tunnel from one qdot to theother and then back. If a pulse having a pulse width of π is applied,the particle travels from one qdot to the next and stops.

A diagram illustrating quantum state superposition of an examplecontrolled semiconductor shift register is shown in FIG. 20B. Beforetime 1195, the control signal V_(IA) applied to the control gate 1193determined the lowering of the tunneling path 1194 barrier for a givenamount of time that corresponds to a phase rotation θ. The result wasthat the quantum particle 1191 was spread between the first twoleft-most qdots 1196, i.e. is in a quantum superposition state 1192. Anequal distribution or an arbitrary one can be achieved with theappropriate control signals. Note that the split may comprise theHadamard state if θ=π/2. Otherwise, any split or rotation may beachieved.

Thus, after the leftmost qdot is initialized, a control gate pulsehaving a pulse width of θ is applied which is different from π or anymultiple of π. This means the particle will be split. The full electronthat initially was in the first qubit is now split between the first andthe second qdot 1192. This is referred to as superposition state of theparticle.

A diagram illustrating shifting of a first component of an examplecontrolled semiconductor shift register is shown in FIG. 20C. At time1206, The quantum state after a first 7C pulse V_(IB), i.e. half theRabi oscillation period, is applied to the second control 1202 terminalis shown. This determines the shifting of the split particle 1201, 1202from the second qdot 1207 to the third qdot as indicated by the arrow1208. The split particle component 1201 from the first qdot 1207 staysin the same position since the control signal V_(IA) keeps its tunnelbarrier high.

Note that subsequently, after applying the third control pulse V_(IC),also of width π or half the Rabi oscillation period, the split particle1202 will travel from the third qdot to the fourth qdot. In response tothe fourth control pulse V_(ID), the split particle will travel from thefourth qdot to the fifth qdot. The control signals are applied signalsone after the other which causes the particle or split particle totravel from one qdot to the other.

A diagram illustrating shifting of a second component of an examplecontrolled semiconductor shift register is shown in FIG. 20D. At time1216, a second pulse V_(IA) of duration π or half the Rabi oscillationperiod is applied to the first control gate 1211. The split particle1212 which was left in the first qdot 1218, is shifted to the secondqdot. The shifting continues by applying the remaining control pulsesV_(IB) and V_(IC). The resulting action is that of a shift registerwhereby one or more particles or split particles are shifted as desired.

Note that although one control pulse was shown active at the given timein the present example, multiple control pulses may be active at thesame time. For example, two control pulses may occur at the same time ondifferent qdots depending on where the two qdots are located. Theresults of applying control pulses to two particles at the same timedepends on the slope. If the slope is relatively steep, i.e. fast, thequantum swap action results. If the slope is gradual, i.e. slow, thenthe quantum annealing gate results. If the two particles are notadjacent to each other, two particles will shift at the same time. Thus,any combination of actions can be achieved.

A diagram illustrating an example of linear, zig-zag, and angledcontrolled quantum shift registers with qubits using tunneling throughoxide layer and planar semiconductor process is shown in FIG. 21A. Thequantum structures comprise a zig-zag or staircased shaped shiftregister 1220, linear shift register 1221, and perpendicular angledshift register 1223. The planar semiconductor quantum shift registerscomprise a plurality of qdots 1222, tunneling 1226 through a thin gateoxide layer, and control gates 1224. The direction of transport of thezig-zag shift register is at an angle, forming a V-shape structure. Thisis advantageous, since it achieves a variable distance to a givenlocation and allows strong interaction for some locations and weak ornegligible interaction for other locations.

A diagram illustrating an example of linear, zig-zag, and angledcontrolled quantum shift registers with qubits using tunneling throughlocal depleted region in a well and planar semiconductor process isshown in FIG. 21B. The quantum structures comprise a zig-zag orstaircased shaped shift register 1230, linear shift register 1231, andperpendicular angled shift register 1233. The planar semiconductorquantum shift registers comprise a plurality of qdots 1232, tunneling1236 through a local depletion region in a semiconductor well undercontrol of a control gate 1234.

A diagram illustrating an example of linear, zig-zag, and angledcontrolled quantum shift registers with qubits using tunneling throughoxide layer and 3D semiconductor process is shown in FIG. 21C. Thequantum structures comprise a zig-zag or staircased shaped shiftregister 1240, linear shift register 1241, and perpendicular angledshift register 1243. The 3D semiconductor quantum shift registerscomprise a plurality of qdots 1242 having fins (wells) 1248, tunneling1246 through a thin gate oxide layer under control of a control gate1244.

A diagram illustrating an example of linear, zig-zag, and angledcontrolled quantum shift registers with qubits using tunneling throughlocal depleted region in a fin and 3D semiconductor process is shown inFIG. 21D. The quantum structures comprise a zig-zag or staircased shapedshift register 1250, linear shift register 1251, and perpendicularangled shift register 1253. The 3D semiconductor quantum shift registerscomprise a plurality of qdots 1252 with fins (well) 1258, tunneling 1256through a local depletion region in a semiconductor fin under control ofa control gate 1254.

Note that shift registers having any geometric shape may be fabricatedusing the four semiconductor processes described supra depending on theconstraints of the semiconductor process used, e.g., linear,rectangular, angular, staircase, V, X, I, H shaped, etc. and theavailable path for the ‘registers’.

A diagram illustrating an example quantum shift register interconnectingquantum interaction gates is shown in FIG. 22. A common use for quantumshift register is shown in this figure. The quantum circuit, generallyreferenced 1260, comprises quantum gates 1262 connected by a quantumshift register 1264. The circuit also comprises quantum cores 1266connected by a plurality of quantum shift registers 1268. Each quantumcore may comprise a plurality of quantum interaction gates 1261 alsoconnected by quantum shift registers 1263.

Normally, quantum operations are performed in quantum interaction gates.The quantum particles/states need to be transported from one quantuminteraction gate to another. This function is performed by quantum shiftregisters. Quantum shift registers are also used to transport quantumparticles/states from one quantum core to another. Thus, both local andglobal transport quantum shift registers are provided.

For example, consider quantum interaction gate #1 and quantuminteraction gate #2. Some particles interact in quantum interaction gate#1 and it is desired to move one of the particles to quantum interactiongate #2 to interact with other particles. A quantum shift register isused to link between different quantum interaction gates and therebymove particles. A quantum shift register also functions to link betweenthe classic world and quantum interaction gates. Since the particle mustbe injected before any kind of interaction, it typically must beinjected before being moved to an interaction qdot.

In the case of a plurality of quantum cores, where each comprises aplurality of quantum interaction gates, each of the quantum interactiongates is linked through shift registers that are relatively small sized.Moving from one quantum core to another, however, typically requireslarger size quantum shift registers. For example, the distance particlesare moved in localized quantum shift registers are in the range ofmicrons. Moving from one quantum core to another, may involve distancesof tens of microns or even hundreds of microns.

A diagram illustrating an example double V quantum structureincorporating quantum shift registers is shown in FIG. 23A. The quantumstructure with tunneling through local depletion regions, generallyreferenced 1270, comprises a double V quantum interaction gate (e.g.,CNOT) with four quantum shift registers 1272 and two interaction qdots.The four shift registers function only to transport the quantumparticles/states in and out of the interaction qdots on either side ofthe quantum interaction gate, i.e. from a remote location to the closelyspaced location where the interaction will take place. Thus, the quantuminteraction gate comprises four ports.

In some cases it is desired to achieve interaction/entanglement betweena plurality of particles/states. A diagram illustrating an examplemultiple V quantum structure incorporating quantum shift registers isshown in FIG. 23B. The quantum structure with tunneling through a localdepletion region, generally referenced 1280, comprises a multiple Vquantum interaction gate with a plurality of quantum shift registers1282 and multiple interaction qdots in three paths. The multiple shiftregisters function to transport the quantum particles/states in and outof the interaction qdots, i.e. from a remote locations to the closelyspaced locations where quantum interaction will take place. Note thatthis example includes two interaction locations or quantum gates. Onebetween the first and second V shape quantum structure and a secondbetween the second and the third V shape quantum structure. In this casean even larger number of quantum shift registers are used to transportthe quantum particles/states between, to, and from the interactionlocations.

A diagram illustrating an example H interaction quantum flow pathincorporating quantum shift registers is shown in FIG. 23C. The 3Dquantum structure with tunneling through a local depletion region,generally referenced 1290, comprises an H shaped quantum interactiongate with a plurality of quantum shift registers 1292 and multiplequantum gates 1294 interaction qdots in three paths. The multiple shiftregisters function to transport the quantum particles/states in and outof the interaction qdots, i.e. from a remote locations to the closelyspaced locations where quantum interaction takes place.

The interaction gates include two qdots placed in close proximity. Therest of the circuitry are the quantum shift registers that are used toshift particles to and from the quantum gates. Note that quantum shiftregister interaction gates may be constructed having any desired shape,e.g., I, T, L shapes, orthogonal, vertical, horizontal, angled, etc.

A diagram illustrating example linear and zig-zag controlled quantumshift registers using tunneling through separate oxide layer is shown inFIG. 24. The linear quantum shift register structure 1300 and zig-zagquantum shift register 1302 are implemented with tunneling through gateoxide. The wells are represented by the empty squares 1301 while thesquares 1305 represent gates that overlap the wells in the corners andsquares 1303 are the control gates. Note that the small overlap betweenthe gate and the well is preferable because a small overlap results in asmall capacitance which makes the Coulomb blockade voltage higher.

A diagram illustrating an example z shift register in planarsemiconductor process using partial overlap of semiconductor well andcontrol gate is shown in FIG. 25. The shift register, generallyreferenced 1320, comprises a plurality of wells 1326 that are separatedand overlapping control gates 1328. The zig-zag quantum shift registeruses tunneling through oxide and half gate length side overlap withhangover. The arrows 1322, 1323 indicate the loading of particles on oneend that are shifted to the interaction qdot 1329. Arrow 1324, 1325represent the path the particle takes after interaction away from theinteraction qdot.

Regarding the semiconductor process of the quantum circuits in FIGS. 24and 25, a particle in one of those qdots of the structure 1320 cannottravel laterally to other qdots because of thick oxide separating thewells, e.g., tens or hundreds of nanometers distance. The only way theparticle can travel is via the gate that overlaps two wells. Thethickness of the oxide between a well and a gate is very small, one ortwo nanometers in current advanced semiconductor processes. Thus, thelateral distance between two wells is tens or hundreds of times biggerthan the vertical distance. Furthermore, the tunneling current dependsexponentially on the thickness of the oxide. Given the gate oxide isaround one or two nanometers and well to well distance is hundreds ofnanometers, tunneling laterally from one well to the other isnegligible. The electron can only tunnel from the well through the gateoxide to the gate then transport through the gate which conducts andthen tunnel through to the other well.

It is noted that the particle, e.g., electron, can be made to tunnel upthrough the oxide through the gate and back down to the other well byappropriately controlling the voltages applied to the control gate andwells. For example, applying a more positive potential on the gate, theelectron will tunnel from the well to the gate. The electron willcontinue to tunnel if a potential that is even more positive is appliedto the well. The potential can be applied in several ways including withanother well, a poly gate, metal that goes on top, etc.

A diagram illustrating an example quantum shift register using qdotsrealized in a planar continuous well with local depletion region andvoltage driven imposing is shown in FIG. 26. The quantum shift register,generally referenced 1310, comprises quantum structure 1311, resetcircuit 1312, injector circuit 1314, imposer circuit 1316, and detectorcircuit 1318. The shift register also comprises interface devices/wells1313, 1315 placed at the two ends of the continuous well to interfacewith classic electronic circuits.

A diagram illustrating an example controlled quantum shift register withauxiliary magnetic field control is shown in FIG. 27. The circuit,generally referenced 1330, comprises a quantum semiconductor shiftregister 1336 realized in a planar process using a long continuous wellwith multiple overlapping control gates that induce local depletionregions in the well. In addition, mixed electric and magnetic fieldcontrol can be used. The magnetic field can be generated with aninductor 1334 or by a resonator 1332. Both local and global magneticcontrol and both static and ac magnetic fields can be used.

When RF current is passed through an inductor 1334, a magnetic field iscreated. This magnetic field can be used to control the quantumstructure. A magnetic field can also be generated by placing the entirestructure or the entire QPU chip in a cavity 1332. Exciting the metalcavity using an amplifier, a magnetic field is generated inside that canbe used to control the quantum structure.

In operation, the depletion regions in the continuous well under thecontrol gates are inducted and by modulating the potential withimposers, the tunnel barriers can be controlled high and low. Thisenables a particle to either tunnel or be blocked from tunneling. Thepotentials used to control the circuit are generated for example byDACs.

A diagram illustrating an example quantum shift register fabricatedusing planar semiconductor process using qubits with tunneling throughseparate oxide layers is shown in FIG. 28A. The quantum structure,generally referenced 1400, comprises a double V shape with qdots thatare completely separated, several quantum shift registers, and at leastone interaction gate in the middle region. The shift registers functionto shift the particles in and out of the quantum interaction gate.

A diagram illustrating an example quantum shift register fabricatedusing planar semiconductor process using qubits with tunneling throughlocal depleted wells is shown in FIG. 28B. The quantum structure,generally referenced 1410, comprises a double V shape with qdotsfabricated on continuous wells, several quantum shift registers, and atleast one interaction gate in the middle region. The shift registersfunction to transport the particles in and out of the quantuminteraction gate.

A diagram illustrating an example quantum shift register fabricatedusing 3D semiconductor process using qubits with tunneling throughseparate oxide layers is shown in FIG. 28C. The quantum structure,generally referenced 1420, comprises a double V shape with qdots havingfins that are completely separated, several quantum shift registers, andat least one interaction gate in the middle region. The control gateoverlaps two fins to allow tunneling from fin to fin through the thingate oxide. The shift registers function to move the particles in andout of the quantum interaction gate.

A diagram illustrating an example quantum shift register fabricatedusing 3D semiconductor process using qubits with tunneling through localdepleted wells is shown in FIG. 28D. The quantum structure, generallyreferenced 1430, comprises a double V shape with qdots having fins,several quantum shift registers, and at least one interaction gate inthe middle region. The control gate overlaps the fins to allow tunnelingfrom fin to fin through a local depletion region in the fins under thecontrol gate. The shift registers function to move the particles in andout of the quantum interaction gate.

As described supra, using the same quantum structure with qdots that arein close proximity and qdots that are far away, virtually any quantumoperation can be achieved depending on how the control pulse signals areprogrammed. One of the operations, the ancillary, is useful forperforming quantum error correction. The simplest ancillary state is theHadamard state. Consider two qdots where a particle is split equallybetween those qdots. The result is an ancillary state that is Hadamarddistributed, meaning it has 50% probability of being in each of the twoqdots.

It is generally well known that a quantum state cannot be copied sinceonce it is copied it is destroyed. Consider a quantum state having anangle φ and an angle θ. This state cannot be duplicated to anotherstructure and have exactly the same angles φ and θ. One of the angles,however, can be replicated. In most cases, the angle replicated is theangle θ that gives the rotation about the z-axis. Thus, although thecomplete quantum state cannot be replicated, a portion of the quantumcan be. This is termed a higher order ancillary.

A diagram illustrating a first example double interaction quantumstructure using a 3D semiconductor process with tunneling through gateoxide is shown in FIG. 29A. The quantum structure, generally referenced1340, comprises two pairs of qdots 1342, namely D_(A), D_(B), D_(C), andD_(D), fins 1346, tunneling path 1348, and control gate 1344. Assumethat qdots D_(A) and D_(B) have some split of electrons 1341, 1343 in aquantum state. It is desired that qdots D_(C) and D_(D) have exactly thesame kind of split, meaning they have the same θ rotation of the vectorthat represents the quantum state. Since the angle φ is not replicated,it will not be the same quantum state but it will have the θ samerotation. This can be achieved using a structure with four qdots andapplying the appropriate control gate signals. If, for example, qdotsD_(C) and D_(D) were initially in a Hadamard state, then they will endup being an inverse of the quantum state of qdots D_(A) and D_(B). Thus,from the perspective of 0 rotation, the qdots D_(A) and D_(B) arereplicated. In actuality, the ancillary state of qdots D_(C) and D_(D)is made to correspond to that of qdots D_(A) and D_(B).

A diagram illustrating a second example double interaction quantumstructure using a 3D semiconductor process with tunneling through localdepletion region is shown in FIG. 29B. The quantum structure, generallyreferenced 1350, comprises two pairs of qdots 1352, namely D_(A), D_(B),D_(C), and D_(D), fins 1353, tunneling path 1354, and control gate 1351.Assume that qdots D_(A) and D_(B) have some split of electrons 1356,1358 in a quantum state. This embodiment is similar to that of FIG. 29Awhere the double interaction yields a higher order ancillary thatreplicates the θ rotation of the vector that represents the quantumstate.

A diagram illustrating a third example double interaction quantumstructure using a planar semiconductor process with tunneling throughgate oxide is shown in FIG. 29C. The quantum structure, generallyreferenced 1360, comprises two pairs of qdots 1363, namely D_(A), D_(B),D_(C), and D_(D), tunneling path 1362, and control gate 1361. Assumethat qdots D_(A) and D_(B) have some split of electrons 1364, 1365 in aquantum state. This embodiment is similar to that of FIG. 29A where thedouble interaction yields a higher order ancillary that replicates the θrotation of the vector that represents the quantum state.

A diagram illustrating a fourth example double interaction quantumstructure using a planar semiconductor process with tunneling throughlocal depletion region is shown in FIG. 29D. The quantum structure,generally referenced 1370, comprises two pairs of qdots 1372, namelyD_(A), D_(B), D_(C), and D_(D), local depletion region 1376, and controlgate 1374. Assume that qdots D_(A) and D_(B) have some split ofelectrons 1371, 1373 in a quantum state. This embodiment is similar tothat of FIG. 29A where the double interaction yields a higher orderancillary that replicates the θ rotation of the vector that representsthe quantum state.

A diagram illustrating an example double V structure incorporatingdouble interaction quantum shift register is shown in FIG. 30. Thequantum structure, generally referenced 1380, comprises a double V shapestructure using a planar semiconductor process with tunneling throughgate oxide. In this embodiment, the control of the structure iselectric, where appropriate control pulses are applied to achieve thedesired quantum operation. Note that the structure in the middle is thequantum gate while the remaining qdots are the shift registers thattransport the particle

A diagram illustrating an example double V structure incorporatingdouble interaction quantum shift register and auxiliary magnetic fieldcontrol is shown in FIG. 31. The quantum structure, generally referenced1390, comprises a double V shape structure 1396 using a planarsemiconductor process with tunneling through local depletion region. Inthis embodiment, the control of the structure is both electric andmagnetic, where appropriate electric control pulses as well as anauxiliary magnetic field are applied to achieve the desired quantumoperation.

Several example quantum structures incorporating double interactiongates are provided. A diagram illustrating an example double V quantumstructure with interaction qdots and shifting qdots is shown in FIG. 32.The quantum structure, generally referenced 1480, comprises fourinteraction qdots in the middle of the structure and shifting qdots thatare part of the quantum shift register that transport the particles inand out of the interaction qdots.

A diagram illustrating an example double interaction quantum structureusing a planar semiconductor process with tunneling through gate oxideis shown in FIG. 33. The quantum structure, generally referenced 1490,comprises four interaction qdots D_(A), D_(B), D_(C), and D_(D) in themiddle of the structure and shifting qdots that make up the quantumshift register that transports the particles in and out of theinteraction qdots.

Note that typically a quantum interaction gate cannot be realized usingonly interaction qdots since a means of shifting the quantum state toand from them is required. If the quantum state is not shifted, then theparticles in the interaction qdots remain in strong interaction and thequantum state cannot be processed. To process the quantum state, thereis a need to move the particles further away from each other whereinteraction is negligible. Thus, the particles are first moved intoclose proximity and then the control gates are exercised to allow themto interact, then they are moved away.

A diagram illustrating an example double interaction quantum structurewith planar semiconductor process using tunneling through oxide is shownin FIG. 34A. The quantum structure, generally referenced 1500, comprisesfour interaction qdots in the middle of the structure. Shifting qdotscan be added on either side of the core qdots that form the quantumshift register that transport the particles in and out of theinteraction qdots.

A diagram illustrating an example double interaction quantum structurewith planar semiconductor process using tunneling through localdepletion region is shown in FIG. 34B. The quantum structure, generallyreferenced 1510, comprises four interaction qdots in the middle of thestructure. Shifting qdots can be added on either side of the core qdotsthat form the quantum shift register that transport the particles in andout of the interaction qdots.

A diagram illustrating an example quantum interaction gate with doubleinteraction and interface devices on either end is shown in FIG. 35. Thequantum structure with planar semiconductor process using tunnelingthrough local depletion region, generally referenced 1520, comprisesfour interaction qdots in the middle of the structure. Shifting qdotscreated by the additional control gates fabricated on the continuouswell are located on either side form the quantum shift register thattransport the particles in and out of the interaction qdots. Inaddition, interface devices 1522, 1524 are located at the left and rightends of the structure.

A diagram illustrating an example controlled quantum shift registerincorporating ancillary gate is shown in FIG. 36A. A diagramillustrating an example controlled quantum shift register with Hadamardof the ancillary register is shown in FIG. 36B. A diagram illustratingan example controlled quantum shift register with loading of the mainstate is shown in FIG. 36C. A diagram illustrating an example controlledquantum shift register performing the ancillary operation is shown inFIG. 36D.

With reference to FIGS. 36A, 36B, 36C, and 36D, the quantum structure,generally referenced 1440, comprises a main state shift register 1444and an ancillary state shift register 1446. Both comprise linear shiftregisters parallel to each other. To achieve the ancillary function in ashift register, one full particle 1442 is loaded in one of the shiftregisters. Then appropriate controls are applied such that the fullparticle is split Hadamard in the ancillary state shift register. Then,in the main state shift register, a given superposition quantum state aand β is shifted. One of the shift registers is Hadamard and the otherone is a precise quantum state α and θ, i.e. the target state. Releasingthe controls for the lower ancillary state shift register causes it togenerate an image corresponding to the θ rotation of the upper mainstate shift register. This results in quantum states α and β in theupper main state shift register and β and α in the lower ancillary stateshift register. Thus, using two shift registers, an ancillary functionis achieved.

Several additional embodiments of quantum shift registers that providethe ancillary function will now be presented. A diagram illustrating anexample quantum structure with double interaction using planarsemiconductor qdots with tunneling through oxide layer is shown in FIG.37A. The quantum structure, generally referenced 1530, comprises fourinteraction qdots in the middle of the structure. Shifting qdots createdby the additional control gates located on either side form the quantumshift registers that transport the particles in and out of theinteraction qdots. In addition, interface devices 1532, 1534 are locatedat the left and right ends of the structure. In operation, the two shiftregisters interact to provide an ancillary gate function. Note that thisstructure is similar to structure 1520 (FIG. 35) described supra.

A diagram illustrating an example quantum structure with doubleinteraction using planar semiconductor qdots with tunneling throughlocal depletion region is shown in FIG. 37B. The quantum structure,generally referenced 1540, comprises a plurality of interaction qdots inthe middle of the structure. Shifting qdots created by the additionalcontrol gates fabricated on the continuous well located on either sideform the quantum shift registers that transport the particles in and outof the interaction qdots. In addition, interface devices are located atthe left and right ends of the structure. In operation, the two shiftregisters interact to provide an ancillary gate function.

Note that although the shift registers shown are relatively long, thesame ancillary function is provided in the middle. The particles areshifted left and right so they are further away to reduce interaction.

A diagram illustrating an example double V quantum structure with doubleinteraction using 3D semiconductor qdots with tunneling through oxidelayer is shown in FIG. 37C. The quantum structure, generally referenced1550, comprises four interaction qdots in the middle of the structure.Shifting qdots created by the additional control gates located on eitherside form the quantum shift registers that transport the particles inand out of the interaction qdots. In operation, the two shift registersinteract to provide an ancillary gate function.

Note that the double V structure can be used to create a CNOT quantuminteraction gate. It can be viewed as two shift registers having twolocations in close proximity that create an ancillary function. If thedouble V structure, however, has two double qdots in close proximity,they preferably have symmetric distribution in order to create the imagequantum state and ancillary function.

Thus, the main difference between the double V structure shown here andthe CNOT double V structure is that the CNOT structure has only twoqdots in close proximity. The structure here has four qdots in closeproximity in a symmetric distribution. This creates two shift registersthat perform the ancillary function in the middle.

A diagram illustrating an example double V quantum structure with doubleinteraction using 3D semiconductor qdots with tunneling through localdepletion region is shown in FIG. 37D. The quantum structure, generallyreferenced 1560, comprises four interaction qdots in the middle of thestructure. Shifting qdots created by the additional control gateslocated on either side form the quantum shift registers that transportthe particles in and out of the interaction qdots. In operation, the twoshift registers interact to provide an ancillary gate function.

In one embodiment, the shift register is split which enables theelectron to go in multiple paths rather than a single path. A simplesplit qdot is shown fabricated in various semiconductor processes in thefollowing figures. In each example embodiment, three qdots are shown. Ina shift register with three qdots and a gate that overlaps all three, anelectron that tunnels the gate can travel in any of the three pathsdepending on an additional control signal.

A diagram illustrating an example quantum bifurcation gate using planarsemiconductor qdots with tunneling through oxide layer and potentialimposing on the qdot well is shown in FIG. 38A. The quantum structure,generally referenced 1570, comprises three qdots, namely qdot #1 1574,qdot #2 1579, qdot #3 1578, control gates 1572, 1571, tunneling path1577, and particle 1576 which can travel to either qdots #2 or #3.

A diagram illustrating an example quantum bifurcation gate using planarsemiconductor qdots with tunneling through local depletion regioninduced by overlapping control gate is shown in FIG. 38B. The quantumstructure, generally referenced 1580, comprises three qdots, namely qdot#1 1581, qdot #2 1583, qdot #3 1584, control gates 1585, 1586, depletionregions 1577, 1578, and particle 1582 which can travel to either qdots#2 or #3. In this embodiment, the second and third qdots share the wellin which two (or more) depletion regions are created. Once the electron1582 is in position, it can travel from qdot #1 to qdot #2 or from qdot#1 to qdot #3 depending on control voltages applied to the two controlgates. Thus, the shift registers are split into two or more paths.

A diagram illustrating an example quantum bifurcation gate using 3Dsemiconductor qdots with tunneling through oxide layer and potentialimposing on the qdot well (or tunneling path) is shown in FIG. 38C. Thequantum structure, generally referenced 1590, comprises three qdots,namely qdot #1 1593, qdot #2 1594, qdot #3 1595, control gate 1591 thatoverlaps all three fins, tunneling path 1592, and particle 1596 whichcan travel to either qdots #2 or #3. In this embodiment, the electroncan enter the shift register on the top and continue traveling to qdot#2 or it can continue on an alternate shift register path to qdot #3.

A diagram illustrating an example quantum bifurcation gate using 3Dsemiconductor qdots with tunneling through local depletion regioninduced by an overlapping control gate is shown in FIG. 38D. The quantumstructure, generally referenced 1600, comprises three qdots, namely qdot#1 1601, qdot #2 1602, qdot #3 1603, control gates 1605, 1606 thatoverlap fins 1607, and particle 1604 which can travel to either qdots #2or #3.

One of the most efficient ways to build a quantum core or fabric isusing a grid configuration in which the qdots are arranged in rows andcolumns. A diagram illustrating an example grid based matrix or fabricquantum computation unit using quantum path merger and/or bifurcationimplemented with a shared qdot and shared tunneling path is shown inFIG. 39. The re-configurable/reprogrammable grid based quantum computingstructure, generally referenced 1610, comprises a plurality of qubits1612 arranged in rows and columns and associated control circuitryincluding control signal generator (not shown). One path comprises inputpath 1611, shared qdot 1614, and multiple output paths 1615. A secondpath comprises input path 1613, shared tunneling path 1616, and multipleoutput paths 1617. Note that the grid array of qubits can bere-programmed to implement other structures and configurations inaccordance with the particular application.

Note that numerous configurations of shift register can be configuredusing a matrix of qdots which form qubits by proper selection. A splitor bifurcated shift register can be configured where the an active qdotcan be shared between multiple qubits in the upper path. Alternatively,bifurcation can be achieved by sharing a tunneling path (i.e. controlgate) between multiple qubits. Thus, there are shift registers thatshare either a quantum well or a quantum gate (i.e. tunneling path)which allows the quantum operation to split.

A diagram illustrating an example reconfigurable quantum computing unitusing memory based reconfiguration control for both reconfigurableaccess control and reconfigurable operation is shown in FIG. 40. Thequantum processing unit, generally referenced 1620, comprises a digitalcontrol (DSP)/quantum processing reconfigurable control unit 1622 incommunication with the external support unit (ESU) 1628, reconfigurableaccess control unit 1623, reconfigurable operation control unit 1625,memory based reconfigurable control unit 1624, and quantum fabric 1627incorporating access control gates 1629 and one or more bifurcations1626.

In operation, consider an algorithm to be executed in the quantum fabricthat is a sequence of quantum operations. The memory basedreconfigurable control unit is loaded with instructions that indicatewhat controls are needed to be active and when in order to select andconfigure the appropriate qubits in the quantum fabric or matrix. Thememory unit stores all the iterations that are required that will act onthe amplitude and pulse width controls as well as the access controlgates of the fabric. The reconfigurable access control unit functions toprovide the control signals to the access control gates in the quantumfabric. The reconfigurable operation control unit functions to providecontrol signals to the qdots and qubits in the quantum fabric. Note thatthe quantum fabric or matric may comprise any combination of quantumstructures.

In accordance with the invention, to create a bifurcation in a shiftregister, either (1) a qdot is shared or (2) a tunneling path (i.e.control gate) is shared. A diagram illustrating example quantumcomputing paths incorporating multiple merging and bifurcations is shownin FIG. 41. The quantum structure, generally referenced 1630, comprisesshared qdots 1632, qdots 1638, access control gates 1634, and accesspaths 1636. In this embodiment, the shared qdots provide cross connectfunctionality to the quantum fabric. Note that any combination ofmerging and bifurcations is possible. In addition, any number ofbranches and bifurcation/quantum demultiplexing and merging/quantummultiplexing can be realized.

A diagram illustrating an example quantum computation path bifurcationand/or merger using a shared access path and indirect potential imposingon the quantum wells to determine the bifurcation/merger function isshown in FIG. 42. The quantum structure, generally referenced 1640,comprises shared qdots 1644, shared tunneling path 1642, potentialimposing wells 1646, and access control gates 1648.

In order to branch a quantum computation path (i.e. bifurcation ormerging), a qdot needs to be shared amongst multiple paths. Either aquantum well is shared or a quantum tunneling path is shared. In thisembodiment, an example of quantum computation path bifurcation and/ormerger using a shared access path (e.g. tunneling path) and indirectpotential imposing on the quantum wells to determine thebifurcation/merger function is provided. The potential imposing on thequantum dots sets the height of the tunneling barriers and thecorresponding tunneling behavior and the resulting quantum operation.

Similar to the embodiments presented supra where the tunneling path wasshared between two or more quantum computation paths, a given well canalso be shared between multiple quantum computation paths. A diagramillustrating an example quantum computation path bifurcation and/ormerging using planar semiconductor qdots with tunneling through oxidelayer is shown in FIG. 43. The quantum structure, generally referenced1650, comprises potential imposing wells 1656, 1658, particle 1654,shared tunneling path (control gate) 1652. The structure providesquantum computation path bifurcation and/or merging using planarsemiconductor qdots with tunneling through an oxide layer using a sharedquantum well that has multiple overlapping gates (tunneling paths).

In this embodiment, the bifurcation is realized in the shift registersincluding a main shift register that goes for example from lower left tothe upper right. The gate 1652 is shared and another segment of shiftregister goes from the center to the lower right. Depending on thecontrol signal pulses applied to the imposing potential wells 1656,1658, the particle 1654 can travel from the center to the upper path orfrom the center to the bottom path. In this manner, a splitting or abifurcation in a shift register is obtained.

A diagram illustrating an example quantum computation path bifurcationand/or merging using planar semiconductor qdots with tunneling throughan oxide layer using shared quantum well with multiple overlapping gatesis shown in FIG. 44. The quantum structure, generally referenced 1660,comprises potential imposing wells 1664, 1666, and shared qdot 1662. Inthis embodiment, the quantum well is shared. Once the particle is in thecenter shared qdot, the particle can move along the shift registereither up or down in accordance with the control signal applied to thetwo gates 1661, 1663.

In some semiconductor processes a continuous well may split in multipledirections. Depending on the design rules and the minimum distancesallowed, a larger quantum well is needed for the shared qdot or a singlesmaller region can be shared. A diagram illustrating a first examplequantum computation path bifurcation/merging using tunneling throughdepletion region and a continuous well that extends in more than twodirections is shown in FIG. 45A. The quantum structure, generallyreferenced 1670, comprises a bifurcation/merger path, shared qdot 1672,and particle 1674 which can either go up or down. In this example, theappropriate control pulses are applied to the shared qdot to steer theparticle in the upward direction as indicated by arrow 1676.

A diagram illustrating a second example quantum computation pathbifurcation/merging using a continuous well that extends in more thantwo directions is shown in FIG. 45B. The quantum structure, generallyreferenced 1680, comprises a bifurcation/merger path, shared qdot 1682,and particle 1684 which can either go up or down. In this example, theappropriate control pulses are applied to the shared qdot to steer theparticle in the downward direction as indicated by arrow 1686.

In the more general case a given quantum path may have both bifurcationand merging from the same shared qdot. A diagram illustrating an examplequantum computation path with both bifurcation and merging using acontinuous well that extends in more than two directions is shown inFIG. 46. The X shaped quantum shift register structure, generallyreferenced 1690, comprises reset circuit 1694, injection circuit 1696,imposing circuits 1698 that go to the different terminals to control thestructure, detector circuits 1691, and interface devices 1693. Thequantum well in the center of the X shaped structure is shared to createthe bifurcation.

In one embodiment, more than three quantum paths may be merged or split.A diagram illustrating an example X shaped (i.e. 4-way) quantumcomputation path with bifurcation and/or merging using planarsemiconductor qdots with tunneling through oxide layer and a commontunneling path shared by multiple quantum wells is shown in FIG. 47. Thequantum shift register, generally referenced 1700, comprises gatesharing where the long gate 1702 overlaps multiple qdots 1704. Once theparticle tunnels to the gate, it can go in the direction of any of theother qdots depending on the potential applied to those qdots. Note thatnumerous shapes can be used when merging or splitting four or morequantum paths.

More than three paths can also be merged or split using a commonlyshared well. A diagram illustrating an example X shaped quantumcomputation path with bifurcation and/or merging using planarsemiconductor qdots with tunneling through oxide layer and a common wellshared by multiple tunneling paths is shown in FIG. 48. The quantumshift register, generally referenced 1710, comprises a shared qdot 1712as opposed to the gate. Here too, the particle can go in the directionof any of the other qdots depending on the potential applied to thoseqdots.

A diagram illustrating an example X shaped quantum computation path withbifurcation and/or merging using planar semiconductor qdots withtunneling through local depletion region and a common well shared bymultiple tunneling paths is shown in FIG. 49. The quantum shiftregister, generally referenced 1720, comprises a shared qdot 1722. Theparticle can go in the direction of any of the other qdots depending onthe potential applied to those qdots.

A diagram illustrating an example multiple X shaped quantum computationpath with bifurcation and/or merging using planar semiconductor qdotswith tunneling through local depletion region and a common well sharedby multiple tunneling paths is shown in FIG. 50. The quantum shiftregister, generally referenced 1730, comprises shared qdots 1732, 1734.In this more complex embodiment, the particle can go in the direction ofany of the other qdots depending on the potential applied to thoseqdots.

Note the distinction between interaction gates and shift registers. Theinteraction gates are formed by multiple paths that are separated. Anelectron cannot travel from one path to the other due to the gapsbetween them. In a shift register, on the other hand, an electrontravels through a path as shown in the example X structures describedherein. Bifurcation is implemented in the shift register. The particlecan have any trajectory. A shift register just transports the particleswithout any interaction.

Interaction can occur, however, if a gate is blocked a gate. In thiscase, two of the wells will be in relatively close proximity. Withreference to FIG. 49, although a shift register with bifurcation isshown, if the particle is not allowed to the middle by keeping the innertwo gates low all the time (i.e. the tunneling barriers are high) thenfour qdots are formed that are linked as indicated by arrows 1725, 1726,and interactions may occur there. Thus, interaction can be achievedbetween any two or more qdots if they are in sufficiently closeproximity. Both shifting of the quantum state and quantum interactionare possible in a shift register as long as the qdots are in closeproximity. The particle must go further out to the extremities of theshift register to no longer have any significant interaction.

Thus, a key differentiator between shift register structures andinteraction structures is that the interaction structures are notlinked. The X structure shift register with a center well andbifurcation provides paths whereby the electron can be shifted from anyqdot to any other qdot. The structure that is not linked is theinteraction gate whereby two or more electrons interact. If access tocertain locations in a shift register are restricted, however, a quantuminteraction gate can be created.

A diagram illustrating an example quantum computation path withbifurcation/merging using 3D semiconductor qdots and tunneling throughoxide layer is shown in FIG. 51A. The structure, generally referenced1740, comprises three qdots 1741, namely qdot #1, qdot #2, qdot #3,potential imposing wells 1747, fins 1743, and control gate 1744. Thestructure shares a tunneling path with potential imposing on the wellwhere electrical control of the tunneling causes bifurcation to theupper path as indicated by arrow 1746. Potential imposing for the tunnelbarrier height setting can be done in a number of ways. In this exampleembodiment, an adjacent well potential imposing is used. The three fins1743 comprise narrow pieces of semiconductor perpendicular to thesubstrate. The three fins are connected to three or more wells with onecontrol gate 1744 that overlaps all of them. Once an electron 1742 hastunneled to the gate, it will travel to one of the fins in accordancewith the control signal pulses and potentials applied to the qdots andcontrol gate.

A diagram illustrating an example quantum computation path withbifurcation/merging using 3D semiconductor qdots and tunneling throughoxide layer is shown in FIG. 51B. The structure, generally referenced1750, comprises three qdots 1751, namely qdot #1, qdot #2, qdot #3,potential imposing wells 1757, fins 1754, and control gate 1756. Thestructure shares a tunneling path with potential imposing on the wellwhere electrical control of the tunneling causes bifurcation to thelower path as indicated by arrow 1758. Once the electron 1752 tunnels tothe control gate, it may then go in the upper or lower directiondepending on the well imposing electrical control signals.

As described supra, semiconductor quantum structures can be controlledwith electric signal or can be controlled with both electric andmagnetic signals. A diagram illustrating an example magneticallycontrolled quantum bifurcation 3D semiconductor quantum gate withtunneling though oxide layer is shown in FIG. 52A. The structure,generally referenced 1760, comprises three qdots 1765, namely qdot #1,qdot #2, qdot #3, potential imposing wells (not shown), fins 1769, andcontrol gate 1763. In this embodiment, an inductor 1764 or resonator1762 is used to create the control magnetic field (arrow 1768) to causetunneling of the electron 1761 to the upper path as indicated by arrow1766. The bifurcation and merging in this case can be controlled by anelectric filed and/or magnetic field. The particle split or the path inthe shift register can be controlled with a magnetic signal. The quantumstructure is placed in an inductor or it a cavity that creates amagnetic field. Depending on the direction of the magnetic field (e.g.,into the page), the electron will go on the upper direction inaccordance with the magnetic field.

A diagram illustrating an example magnetically controlled quantumbifurcation 3D semiconductor quantum gate with tunneling though oxidelayer is shown in FIG. 52B. The structure, generally referenced 1770,comprises three qdots 1775, namely qdot #1, qdot #2, qdot #3, potentialimposing wells (not shown), fins 1779, and control gate 1773. In thisembodiment, an inductor 1774 or resonator 1772 is used to create thecontrol magnetic field (arrow 1778) to cause tunneling of the electron1771 to the lower path as indicated by arrow 1776. The bifurcation andmerging in this case can be controlled by an electric field and/ormagnetic field. The particle split or the path in the shift register canbe controlled with a magnetic signal. The quantum structure is placed inan inductor or it a cavity that creates a magnetic field. Depending onthe direction of the magnetic field (e.g., out of the page), theelectron will go on the lower direction in accordance with the magneticfield.

A diagram illustrating an example quantum computation path withbifurcation/merging using 3D semiconductor qdots and tunneling throughoxide layer is shown in FIG. 53. The structure, generally referenced1780, comprises qdots 1782 and control gates 1784. It uses both sharedtunneling paths and shared semiconductor fin 1786.

A diagram illustrating an example quantum computation path withbifurcation/merging using 3D semiconductor qdots and tunneling throughoxide layer is shown in FIG. 54. The structure, generally referenced1790, comprises qdots 1799, control gates 1791, 1792, 1793, metalcontacts 1798. It uses shared tunneling paths with potential imposing onthe tunneling path (i.e. control gate) and has several fins with controlgates overlapping them.

Note that a similar quantum structure is also possible with potentialimposing on the well. Note also that each gate needs to haveconnectivity (not shown) for the auxiliary classic electronic circuitsthat perform reset, inject, impose and detect functions of the quantumstates as well as interface devices.

A diagram illustrating an example quantum computation pathmerging/bifurcation gate using 3D semiconductor qdots with tunnelingthrough oxide layer is shown in FIG. 55. The quantum shift registerstructure, generally referenced 1800, comprises a plurality of qdots1802, fins 1806, control gates 1804, and central shared qdot 1802.

A diagram illustrating an example quantum computation path with bothmerging and bifurcation gates using 3D semiconductor qdots withtunneling through local depletion region is shown in FIG. 56. Thequantum shift register structure, generally referenced 1810, comprises aplurality of qdots 1816, fins 1817, control gates 1818, bifurcation qdot1812, and merging qdot 1814.

A diagram illustrating an example controlled quantum shift register withbidirectional flow is shown in FIG. 57. The I shaped linear shiftregister, generally referenced 1820, is implemented with planarsemiconductor process using tunneling through oxide and comprises qdots1824, gate oxide 1823, interaction qdots 1825, and control terminals1822 (potential well imposing). In this embodiment, the shift registeroperates as an interaction as well as a shift register. A barrier placedin the middle of the shift register is configured to always be high.Thus, shifting particles 1821 from either end towards the interactionqdots allows them to interact in the middle. After interacting, theparticles are then shifted away.

A diagram illustrating an example multiple V controlled quantum shiftregister structure is shown in FIG. 58. The quantum shift registerstructure, generally referenced 1830, is fabricated using 3Dsemiconductor process using tunneling through local depletion region. Inthis embodiment, the shift register includes multiple interactionsbetween different shift registers.

A diagram illustrating an example double V controlled quantum shiftregister in a resonator or inductor based magnetic field control isshown in FIG. 59. The quantum shift register structure, generallyreferenced 1840, is fabricated using planar semiconductor process usingtunneling through local depletion region and comprises two shiftregisters 1846, inductor 1844, and resonant cavity 1842. In thisembodiment, interaction between the shift registers occurs which iscontrolled both electrically and by an auxiliary magnetic fieldgenerated by the inductor and/or cavity.

A diagram illustrating an example double V controlled quantum shiftregister using planar semiconductor process with tunneling through oxidelayer is shown in FIG. 60. The quantum shift register structure,generally referenced 1850, comprises interaction in a quantum gate and aplurality of quantum transport qdots.

A diagram illustrating an example controlled quantum shift registerusing planar semiconductor process with tunneling through local depletedwell is shown in FIG. 61. The quantum shift register structure,generally referenced 1860, comprises multiple quantum interaction gates1862, 1864 and multiple quantum transport qdots 1866 creating aplurality of flow paths. It is appreciated that the structure can haveany kind of shape and the shift registers can be realized withrelatively arbitrary, non-uniform shapes.

A diagram illustrating an example controlled quantum shift registerusing planar semiconductor process with tunneling through oxide layer isshown in FIG. 62. The quantum shift register structure, generallyreferenced 1870, comprises multiple quantum interaction gates andmultiple quantum transport qdots creating a plurality of flow paths.

A diagram illustrating an example controlled quantum shift registerusing 3D semiconductor process with tunneling through local depletedwell is shown in FIG. 63. The quantum shift register structure,generally referenced 1880, comprises multiple quantum interaction gates,multiple quantum transport qdots creating a plurality of flow paths, andone or more quantum bifurcation qdots.

A diagram illustrating an example controlled quantum shift registerusing 3D semiconductor process with tunneling through oxide layer isshown in FIG. 64. The quantum shift register structure, generallyreferenced 1890, comprises multiple quantum interaction gates, multiplequantum transport qdots creating a plurality of flow paths, and one ormore quantum bifurcation qdots.

Those skilled in the art will recognize that the boundaries betweenlogic and circuit blocks are merely illustrative and that alternativeembodiments may merge logic blocks or circuit elements or impose analternate decomposition of functionality upon various logic blocks orcircuit elements. Thus, it is to be understood that the architecturesdepicted herein are merely exemplary, and that in fact many otherarchitectures may be implemented which achieve the same functionality.

Any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality may be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermediary components. Likewise, any two componentsso associated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundariesbetween the above described operations merely illustrative. The multipleoperations may be combined into a single operation, a single operationmay be distributed in additional operations and operations may beexecuted at least partially overlapping in time. Moreover, alternativeembodiments may include multiple instances of a particular operation,and the order of operations may be altered in various other embodiments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim. The use of introductory phrases suchas “at least one” and “one or more” in the claims should not beconstrued to imply that the introduction of another claim element by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim element to inventions containing only one suchelement, even when the same claim includes the introductory phrases “oneor more” or “at least one” and indefinite articles such as “a” or “an.”The same holds true for the use of definite articles. Unless statedotherwise, terms such as “first,” “second,” etc. are used to arbitrarilydistinguish between the elements such terms describe. Thus, these termsare not necessarily intended to indicate temporal or otherprioritization of such elements. The mere fact that certain measures arerecited in mutually different claims does not indicate that acombination of these measures cannot be used to advantage.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. As numerousmodifications and changes will readily occur to those skilled in theart, it is intended that the invention not be limited to the limitednumber of embodiments described herein. Accordingly, it will beappreciated that all suitable variations, modifications and equivalentsmay be resorted to, falling within the spirit and scope of the presentinvention. The embodiments were chosen and described in order to bestexplain the principles of the invention and the practical application,and to enable others of ordinary skill in the art to understand theinvention for various embodiments with various modifications as aresuited to the particular use contemplated.

What is claimed is:
 1. A quantum shift register, comprising: asemiconductor substrate; a plurality of quantum wells fabricated on saidsemiconductor substrate forming a plurality of quantum dots arranged insequential fashion; an oxide layer fabricated over said plurality ofquantum wells; a plurality of substantially floating gates fabricatedover said oxide layer and at least partially overlaying said pluralityof quantum wells, each floating gate operative to provide conductiontransport of a quantum particle between adjacent quantum wells viatunneling through said oxide layer; and a plurality of control gateselectrostatically coupled to said plurality of floating gates, wherebyelectric control gate pulses applied to said plurality of control gatescontrol said floating gates between neighboring quantum dots such thatone or more particles within said quantum dots are transported from onequantum dot to another.
 2. The shift register according to claim 1,wherein said plurality of electric control gate pulses are generated byclassic electronic circuitry.
 3. The shift register according to claim2, wherein said classic electronic circuit comprises one or more digitalto analog converters (DACs).
 4. The shift register according to claim 1,further comprising one or more quantum gates, at least one quantum gatebeing in relatively close proximity to another quantum gate in a same orseparate quantum shift register to enable quantum interaction betweenparticles therebetween.
 5. The shift register according to claim 1,wherein one or more quantum tunneling paths are controlled viaappropriate application of electric control gate pulses to said controlgates thereby controlling movement of said one or more particles intoand out of one or more interaction quantum dots.
 6. The shift registeraccording to claim 1, wherein said plurality of quantum dots areconstructed using a semiconductor process selected from a groupconsisting of: a planar quantum structure using tunneling through anoxide layer and a 3D quantum structure using tunneling through an oxidelayer.
 7. A quantum shift register, comprising: a semiconductorsubstrate; a plurality of quantum wells fabricated on said semiconductorsubstrate forming a plurality of quantum dots arranged in sequentialfashion; an oxide layer fabricated over said plurality of quantum wells;a plurality of substantially floating gates fabricated over said oxidelayer and at least partially overlaying said plurality of quantum wells,each floating gate operative to provide conduction transport of aquantum particle between adjacent quantum wells via tunneling throughsaid oxide layer; a plurality of control gates electrostatically coupledto said plurality of floating gates, whereby electric control gatepulses applied to said plurality of control gates control quantumtunneling paths between neighboring quantum dots such that one or moreparticles within said quantum dots are transported from one quantum dotto another; and an auxiliary magnetic field covering at least saidplurality of quantum dots and operative to provide additional control onsaid plurality of quantum dots.
 8. The shift register according to claim7, wherein said auxiliary magnetic field is generated utilizing one ormore inductors.
 9. The shift register according to claim 7, wherein saidone or more magnetic fields are generated utilizing one or moreresonators.
 10. The shift register according to claim 7, wherein saidplurality of electric control gate pulses are generated by classicelectronic circuitry.
 11. The shift register according to claim 10,wherein said classic electronic circuit comprises one or more digital toanalog converters (DACs).
 12. The shift register according to claim 7,further comprising one or more quantum gates, at least one quantum gatein relatively close proximity to another quantum gate to enable quantuminteraction therebetween.
 13. The shift register according to claim 7,wherein one or more quantum tunneling paths are controlled viaappropriate application of electric control gate pulses to said controlgates thereby controlling movement of said one or more particles intoand out of one or more interaction quantum dots.
 14. The shift registeraccording to claim 7, wherein said plurality of quantum dots areconstructed using a semiconductor process selected from a groupconsisting of: a planar quantum structure using tunneling through anoxide layer and a 3D quantum structure using tunneling through an oxidelayer.
 15. A quantum shift register method, comprising: providing asemiconductor substrate; fabricating a plurality of quantum wells onsaid semiconductor substrate to form a plurality of quantum dotsarranged in sequential fashion; fabricating an oxide layer over saidplurality of quantum wells; fabricating a plurality of substantiallyfloating gates over said oxide layer and at least partially overlayingsaid plurality of quantum wells, each floating gate operative to provideconduction transport of a quantum particle between adjacent quantumwells via tunneling through said oxide layer; and fabricating aplurality of control gates, said plurality of control gateselectrostatically coupled to said plurality of floating gates, wherebyelectric control gate pulses applied to said plurality of control gatescontrol the floating gates between neighboring quantum dots such thatone or more particles within said quantum dots are transported from onequantum dot to another.
 16. The method according to claim 15, furthercomprising generating an auxiliary magnetic field covering at least saidplurality of quantum dots and operative to provide further control ofsaid control gates such that one or more particles within said quantumdots are transported sequentially from one quantum dot to another. 17.The method according to claim 15, wherein said electric control gatepulses are generated using classic electronic circuitry.
 18. The methodaccording to claim 17, wherein said classic electronic circuit comprisesone or more digital to analog converters (DACs).
 19. The methodaccording to claim 15, wherein said plurality of quantum dots areconstructed using a semiconductor process selected from a groupconsisting of: a planar quantum structure using tunneling through anoxide layer and a 3D quantum structure using tunneling through an oxidelayer.
 20. A quantum shift register, comprising: a semiconductorsubstrate; a plurality of semiconductor fins fabricated on saidsemiconductor substrate; oxide fabricated over said plurality ofsemiconductor fins; a plurality of floating gates, each floating gate atleast partially overlapping a pair of neighboring semiconductor fins toform a plurality of quantum dots arranged sequentially, each floatinggate operative to provide conduction transport of a quantum particlebetween adjacent quantum dots via tunneling through said oxide layer;and a plurality of control gates electrostatically coupled to saidplurality of floating gates, whereby electric control gate pulsesapplied to said plurality of control gates control said floating gatesbetween neighboring semiconductor fins such that one or more particleswithin said quantum dots are transported from one quantum dot toanother.
 21. The shift register according to claim 20, furthercomprising one or more quantum gates, at least one quantum gate inrelatively close proximity to another quantum gate in a same or separatequantum shift register to enable quantum interaction between particlestherebetween.